![Thumbnail: [Volume 87, 1959 page 88]](/journals/rsnz/images/rsnz_87/thumbnails/rsnz_87_01_0111_0088_ac_02.gif)
Summary
(i) Line-caught specimens of Centroscymnus crepidater (Bocage & Capello, 1864) and C. owstonii Garman, 1906 from 500 and 600 fathoms respectively off Kaikoura, New Zealand, are recorded and described. Both species can now be regarded as bipolar, C. crepidater being previously known only from the North Atlantic, and C. owstonii from Japan.
(ii) Dermal denticles of juvenile, intermediate and adult types are all present on the specimen of C. owstonii (an immature female 584 mm long), thus confirming that this species undergoes successional growth changes of the denticles similar to those of C. coelolepis Bocage & Capello, 1864. Juvenile and intermediate denticles are strongly tridentate and ridged, the juvenile denticles smaller than the intermediates but with a relatively longer median tooth half or more of the length of the blade Adult denticles first appear on the caudal peduncle where they are weakly tridentate (the median tooth only one-fifth or less of the length of the blade) and lack ridges.
(iii) Embryos of C. crepidater have strongly tridentate and ridged denticles in which the median tooth is half to three-fifths the length of the blade. Adult denticles of C. crepidater are also tridentate and ridged, but with a shorter median tooth (one-quarter to one-third the length of the blade), and additional lateral ridges.
(iv) Embryos of C. crepidater are compared with the description of the juvenile and only specimen of C. rossi (Alcock, 1898) of the Indian Ocean, which has
![Thumbnail: [Volume 87, 1959 page 89]](/journals/rsnz/images/rsnz_87/thumbnails/rsnz_87_01_0112_0089_ac_02.gif)
similarly long preoral clefts. The embryos show a closer resemblance in their proportions to C. rossi than do the adults, and it is suggested that C. rossi may represent a growth stage of C. crepidater.
(v) Diagnostic criteria for separating Centroscymnus from Scymnodon are available in the dermal denticles. In all except the most juvenile specimens of Centroscymnus the denticles are subcircular with a large median concavity on their outer surface near the anterior end; if longitudinal ridges are present the median ridge is restricted to the posterior half or two-thirds, and behind the concavity. By comparison the denticles of Scymnodon are subovoid, with a longer median ridge so that a median concavity is lacking or not conspicuous.
(vi) The degree of obliqueness of the lower teeth is shown to be too variable to be relied on for distinguishing Centroscymnus from Scymnodon.
(vii) The inclusion of Centrophorus plunketi Waite, 1910 in Centroscymnus by Bigelow & Schroeder (1957) is not tenable; the nature of the upper teeth and the dermal denticles refer this species to Scymnodon.