314 Bashford Dean Memorial Volume 



(Text'figure 31) with that of C. anguineus (Text-figure 10) shows that in front view 

 the tooth of tohleri is somewhat like that of anguineus in having a central cusp, with 

 very small slender secondary cusps separating it from the two large lateral ones. How- 

 ever, the whole tooth (as shown in the drawing) has an enormously broad base, unlike 

 that of anguineus; the large cusps are stiff and blunt, while the secondary cusps are very 

 slender compared to the short blunt ones of a?:guineus. 



The teeth of C. tohleri (central cusp) are markedly larger than those of C. anguineus 

 (6 mm. as compared with our average of 4.8 mm.). They are slightly shorter than those of 

 C. lawleyi, which are 7-5 mm. long in Lawley's lithographed plate, where they are marked 

 "grand, nat." 



CLASSIFICATION OF THE FRILLED SHARK 



The outcome of investigations as to the relationships of Chlamydoselachus has 

 been to establish the family to which our shark belongs, and to determine its relationships 

 to the other primitive sharks, Hexanchus, ?iptorhynchus {?{ptidanus) and Heptranchias 

 (Heptanchus). These latter are all included by Carman (1913) in his family Hexeptranchi- 

 dae, which with the family Chlamydoselachidae constitutes the very primitive selachian 

 group Hexanchoidei. We feel that we cannot do better than to quote Carman's (1913) 

 brief statement of family and generic characters. 



Family CHLAMYDOSELACHIDAE 



Carman assigns the family characters in the following concise terms : 



Body elongate, slender. Head broad, depressed. Eyes lateral, without a nictitating 

 membrane. Nostrils distinct from the mouth. Mouth anterior, without labial folds; teeth 

 with broad, backward-extended bases and slender cusps. Spiracles small. One dorsal [fin], not 

 preceded by a spine. An anal fin. No pits at the root of the caudal. Margin of first gill cover 

 free across the isthmus. Intestine with a 'spiral valve. Pterygoquadrate not articulated to 

 postorbital process of the skull [cranium], hyomandibular elongate. 



Cenus chlamydoselachus 



The family Chlamydoselachidae is monogeneric, and here follows Carman's brief 

 characteri2,ation of the solitary genus: 



Six gill openings, margin of first free across the isthmus. Mouth very wide, longer than 

 the skull, without labial folds. Teeth raptorial, similar in the two jaws, each with a broad 

 base and three slender, curved, subconical cusps, with or without rudimentary cusps at 

 their bases, no median teeth in the upper series; a median series on the symphysis below. 

 Eyes lateral, elongate. Fins broad, caudal [usually] without a notch. 



Species : tobleri, lawleyi and akguihevs 

 C. TOBLERI. — A recently determined species based on a single tooth collected in the 

 Tertiary of the island of Trinidad, Lesser Antilles. The tooth is differentiated from 

 that of the present-day form mainly by the broad base and by the presence of the 

 needle-like secondary cusps. 



