lateral to the apertures: mucous glands everywhere more numerous than the segments, crowded and not circular in outline, median teeth of both series, bifid distally;

Genotype: Myxine biniplicata Richardson and Jowett, 1951.

Additional Data And Corrections To The Description of Neomyxine biniplicata (Richardson and Jowett.)

The following data is drawn from seven specimens ranging in total length from 320 mm. to 412 mm. An eighth specimen, received frozen, of 345 mm. was eleared in hydrochloric acid which for a time revealed the mucous glands, and the count from this specimen is included below in that section. This cleared specimen showed rays in the caudal and anal fins, in the latter to the posterior margin of the cloacal aperture, and a complete absence of rays from the precloacal (ventral) fin-fold.

The distance from the tip of the rostrum to the first gland in the mucous gland series is from 23% to 29% of the distance from the tip of the rostrum to the rear margin of the branchial aperture. The latter distance, the length of the head and pharynx combined, is from 23% to 26% of the total length. The abdominal region taken here as from the posterior margin of the branchial aperture to the posterior margin of the cloacal aperture, is from 57% to 66% of the total length; but of the seven specimens, six fell in a range of from 57% to 61%. The caudal region, which was measured from the posterior end of the cloaeal aperture to the tip of the tail, was 13.6% to 16.5% of the total length. The sectional dimensions are difficult to describe. With this series of specimens laid out, it is obvious that two are deeper and heavier in the body than are the other five, and this extra depth is shown over the greater length of the body, but otherwise there are no particular features which distinguish these two specimens from the others. At the same time, this difference when expressed in percentages of the various body regions is not great. The five specimens range in length from 320 mm. to 412 mm. and in these the depth of the body at the level of the branchial aperture is from 11.0 mm. to 13.0 mm., the width at this point being from 9.0 to 11.0 mm.—i.e., some 2.0 mm. to 3.0 mm. less than the depth. The depth is from 12.4% to 15.6% of the length from the tip of the rostrum to the posterior margin of the branchial aperture. The other two specimens are 343 mm. and 370 mm. in length, within the range of the above. The depth at the branchial aperture is in the smaller, 13.0 mm. and 15.0 mm. in the larger which is 16.0% and 17.0% of the length of the head and pharynx combined. The width at this level does not show the same variation but falls within the range of from 11.5% to 13.2% for all seven specimens. The depth of the body in the abdominal region appears greater than at the rear of the pharyngeal region; but this is due to the presence of the ventral (precloacal) fin-fold. In all specimens, the depth of the body in the abdominal region measured within 1.0 mm. of the depth at the rear of the pharynx. The depth of the ventral fold in the five more cylindrical specimens is 16.8% to 23% of the depth of the body. In the smaller of the two deeper-bodied specimens, this fold is but little more, being 26.5% of the depth; but in the specimen which is 370 mm. long, the fold is 40% of the total depth at this level. The collectors did not remark on these differences and there is the probability that this extremely deep ventral fold may be a consequence from preservation.

The unique lateral fin-folds which extend on either side of the branchial apertures commence at a level between the 29th to 35th of the mucous gland series which is from 75% to 89% of the distance between the tip of the rostrum and the posterior margin of the branchial apertures—i. e., they commence at or in the last quarter of the length of this region. In four of the specimens, this is between 83% to 85% of this distance which is probably the more correct range since, as described in the original account, preservation tends to produce a folding of the skin extending these fin-folds anteriorly so that in the preserved specimen an accurate origin cannot be reliably determined. Some variation in the level of origin is possibly indicated in relation to the mucous glands. Where these could be determined, the fin-fold originated at a level 80% as by count of pores of the glands in the head and pharyngeal series. The length of the folds is equal to the space occupied by 9 to 12 glands and ranges from 19·5% to 27.0% of the distance between the tip of the rostrum and the rear margin of the branchial apertures. In none do the fins meet behind the branchial apertures or join the ventral precloacal told. The latter has been extended between and anterior to the branchial apertures in three specimens, but in life it has its origin immediately posterior to these apertures and extends to the cloacal aperture at a uniform height. There are no rays in this fold. There is no indication of a median dorsal ridge or fold on the abdominal region in life. The dorsal margin of the caudal commences above the 6th to 11th last mucous gland, 54% to 78% of the distance between the rear margin of the cloacal aperture and the tip of the tail, but in five of the specimens this is 54% to 60% of this distance, suggesting that in the two specimens where this was 72% and 78% the true length of this fin may have been altered by preservation. This fold and the anal fold contain rays; in the latter rays are present to the margin of the cloaca.

The determination of the number of mucous glands was not possible in all specimens, and in particular these were obscure in three specimens brought ashore frozen; but in one of the latter treated with hydrochloric acid, the pores and glands become obvious during metaproteinization when the body tissues had swollen and become partially transparent. A full count of glands on both sides was possible with four specimens. These showed an average of 164 on the left, ranging from 152 to 171; and an average of 168 on the right side, ranging from 159 to 175. In these the count of the right side exceeded that of the left by 3 to 7. Complete counts were possible on the left side of two other specimens. These were 148 and 170. Using all available data from these specimens, the number of glands in the various body regions can be summarised as follows:—

• (a) Pharyngeal region, number of glands back to the anterior edge of the branchial aperture, on left side (7 specimens), ranging from 36 to 44, with an average of 40; right side (5 specimens), 36 to 45, and an average of 40.

• (b) Abdominal region, number of glands from anterior edge of branchial aperture to anterior edge of cloacal aperture, on the left side (6 specimens) ranging from 91 to 107, with an average of 100; on the right side (6 specimens), a range of 96 to 105, with an average of 103.

• (c) Caudal region as taken from the anterior margin of the cloacal aperture and counted to the last gland, on the left side (8 specimens), a range of 20 to 24 and an average of 21; on the right side (7 specimens), a range of 20 to 23, and an average of 21.