Classification.

Mr. Brookes has supplied me with four examples of this shell, one a disarticulated paratype (one of the original two specimens) from the collection of the late Mr. J. C. Anderson, now in the collection of Brookes. (2) A very fine specimen in spirit. (3 and 4) Dry, more or less damaged specimens.

For the purpose of comparison with the genus Tonicia, I disarticulated an example from my own collection of T. elegans, the type species of that genus. All valves have strongly pectinated insertion-teeth; the lateral areas and the end-valves bear radiating rows or bands of eye-dots, and the gills extend the whole length of the foot.

I also disarticulated an example of Lucilina suezensis, the type of that subgenus, and found that the insertion-plates were similar to those of the genus Tonicia; the only distinction seems to be the position of the mucro in the tail-valve, certainly a non-generic character, and at most can only warrant subgeneric distinction. In the genus Onithochiton, the insertion-plate of the anterior valve is pectinated like Tonicia, but the insertion-plate of the tail-valve is reduced to a low, smooth and narrow callus. In Suter's Tonicia cuneata, the insertion-plate of the anterior valve is quite dissimilar from that of the three genera above referred to, the teeth being unpectinated and sharp, also the gills do not extend the full length of the body. The minute “eyes” mentioned by Suter are present in all valves, but the larger of these apertures has a diameter of only about 12.5 mmm., whereas in Tonicia they have a diameter of about 50 mmm., and in Onithochiton scholvieni of about 25 mmm. (these measurements are my own); thus it will be noted that whatever may be the function of these “eye-dots” in cuneata, they are much smaller than the typical “eyes” of other genera. We are therefore able to determine that the insertion-plate of cuneata is certainly Acanthoid in character, though the four to five variable slits, instead of the typical 5 slits of the Acanthochitoninae, and the existence of numerous “eye-dots,” separate it from that subfamily. We certainly are justified in its inclusion under the