COCHLIOBOSTIDJ!. 
169 
present in the mandible. Q’eeth with broad, backwardly-extendod 
bases, overlapping ; crown consisting of three slender, curved, sub- 
conical cusps, separated by a pair of rudimentary denticles. Noto- 
chord mainly persistent, in part replaced by feeble cyclospondylic 
vertebral centra. 
A nearly complete description of the t)-pe specimen (female) of the 
single known living species, C. anf]uinett$, from Japanese sea.s, is 
given by S. Garman in the BuU. ifuReum Comp. Zoology, Harvard 
College, vol. xii. no. i. (1885). Further notes, and a large figure, 
are published by A. Gunther, Rep. Deep-Sea Fishes (‘ Challenger ’ 
Reports, vol. xxii. 1887, p. 2, pi. Ixiv.). 
Only one fossil species has hitherto been recorded, and this merely 
upon the evidence of detached teeth: — 
Chlamydosdache lawleyi, J. W. Davis, Proc. Zool. Soc. 1887, 
p. 542 ; ineerto! xedis, R. Lawley, Nuovi Studi sopra ai 
Pesci, etc., delle Collinc Toscane, 1876, p. 87, jd. i. fig. I. 
— Pliocene ; Tuscany. 
Division B. — Two dorsal fins present ; gill-clefts 
five in number. 
Family COCHLIODONTID^. 
An imperfectly definable family, apparently related to the Cestra- 
ciontida;, but with a more specialized dentition. At least one of 
the transverse series of teeth encircling each ramus of the jaw is 
fused into a continuous curved plate, sometimes with an even coronal 
surface, sometimes with ridges and furrows marking the boundaries 
of its components ; this plate increasing in size by additions to its 
inner margin, and the outer border graduallj' coiling inwards instead 
of becoming detached. The root and the crown are approximately 
of corresponding thickness, the attached surface of the former 
being thus almost parallel to the coronal contour. Coronal surface 
punctate, the punctations having no relation to the extremities of 
the vertical medullary canals *. 
The priucipal forms of teeth of this family were originally referred 
by Agassiz “ to Psammodus, and placed with this genus in the family 
of Cestraciontidffi. Somewhat later, the same author recognized at 
least their generic distinctness, first founding the genera Helodus 
' E. Owen, Odontography, vol. i. p. .'59. 
* Poisa. Foss. vol. iii. pis. xiv., xv. 
