32 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY- -IV. 



30. miCRISTODFS (Jill, 1865. 

 iCill, Pror. Ac. Nat. Sri. Phila. 1 >(>">. 1??: ( Mtcrixloilux piniclnliin (>\}\.) 



V 



Tliis ^enns is known from its teeth only. Th'-se are described ;is fol- 

 lows: ''The teeth are fixed and extremely minute, the largest little 

 more ihiin a line in length (in a shark 20 feet lonii') and decrease 

 towards the ends of the jaw; they are disposed in regularly transverse 

 rows. of which there are Hi4 to 1G7 on each side, while in front there 

 are l.'J to 1<> in each transverse row ; each tooth is recurved backwards 

 and acutely pointed, swollen and with a heel-like projection in front 

 rising from its base.' 1 (Gill.) (//.'x/cx)-, small; 'cr-u-, an upright projection; 

 dou?, tooth.) 



4O. 31. GMiiirfatus Gill. 



A very lar^e spotted shark found in the. Gulf of California. (Gill, 

 Proc. Ac. Xat. Sci. Phila. ISiKi, 177.) 



FAMILY XIV. HETERODONTIIbE. 

 (The Port Jackson Xlinrks.) 



Sharks with two dorsal tins, both provided with spines ; the first dor- 

 sal opposite to the space between pectorals and ventrals: the second in 

 advance of I lie anal. Body elongated, obtusely trihedral, gradually taper- 

 ing from the anal region towards the caudal fin; head high, with the fore- 

 head declivous, little prominent; nostrils continent with the mouth; 

 month rather narrow, the upper lip divided into seven lobes, the lower 

 with a fold : spiracles small, below the lower part of the eye ; no nictitat- 

 ing membrane; ^ill-openings rather narrow; dentition similar in both 

 jaus, vi/, small obtuse teeth in front, which in the yon nu are pointed. 

 and pro\ ided with three to five cusps; the lateral teeth lar^e, pad-like, 

 twice as broad as lon>-, arranged in oblique series, one series beiii^ formed 

 by much larger teeth than those in the other series; caudal fin moderate. 

 (ienera 1. L', or.'J; s]>ecies about h inhabit in-' the I'acilic ( >cean. Of much 

 interest to palaeontologists from their supposed relation focertain extinct 

 tyjies. ^('cnlritriiHiliild- Giinlher, \'iii, 117, -IIS; but H<'lcr(l<mtti* has 

 priority over Ccxl radon.) 



I'.ranrliial rr^iiui longer I lian lii^li, tin- >lils liciiii; lil t lr rlou^a i nl : nn-lar irdli Hal 



anil cloM-lv riinlij;-||uM( .................................... (iVI.MIM I I |;< )DI 'S. ',\\ . 



si. GVKOFI>KI;KODIIS cm. 



i. ill, I'l.ic. .\i . Nat. Sri. I'hila. i-ii'j, i-'.t; tyi" 1 Ceatroaon fraaiciaci 



The characters distin^iiishiiii;- this ^roiip from IlrlcnxlontiiK are thus 

 jiiven by Professor (Jill: 



