Hdlocephali — Chivia'roidei. 



93 



fossils, those named Carcliarodoumegalodda (Fig. 127) having an 

 ahnost world-wide distribution. Specimens are exhibited from 

 New Zealand, Australia, South Carolina, the West Indies, 

 France, Spain, Italy, Malta, and Arabia, as also from the 

 Antwerp and Suffolk Crags. The Cai'chariidse are almost, if 

 not exclusively, Tertiary, and only a small collection of teeth of 

 Galeocerdo, Garcharias, Hemipristis, etc., is exhibited. 



It may be interesting to add that in some places, both in the 

 Atlantic and Pacific (especially at extreme depths in the red-clay 

 areas), the " Challenger " dredged up many teeth of Sharks and 

 ear-bones of Whales, all in a semi-fossil state, and usually im- 

 pregnated with oxides of iron and manganese. The Sharks' 

 teeth belong principally to species believed to be extinct, and 

 resemble those found fossil in the late Tertiary formations. 



Sub-class IL— HOLOCEPHALI. 



Okdkk I. — Chimaeroidei. 



The Chiniferas resemble the Sharks in many important ^rr ,^ 

 1 T i • ii 1 11 ji • • f 1 • 1 1 wTalJ-case. 



features, but, m the skull, the upper jaw is fused with the No. 3, and 



cranial cartilage, not suspended by the upper part of the hyoid Table-case, 

 arch. The skeleton is wholly cartilaginous, and the notochord 

 is tolerably persistent, the vertebrae being represented by mere 

 slender rings. In the two living genera, there is a strong- 

 spine in front of the dorsal fin : the gill-clefts are covered by a 

 fold of skin, so that only a single external opening is observed : 

 and the dentition consists of four plates above and two below. 



Teeth of Rhyiu-Jiodus and Palceumyhof from the Devonian of 

 North America, and of Pfijctodns from the Devonian of Russia, 

 are the earliest fossils hitherto definitely referred to this sub- 

 class, but there are no examples in the Collection. The early 

 Jurassic family of Squaloraiida? is represented by the unique 

 genus Squaloraja, of which several fine specimens are exhibited 

 from the Lower Lias of Lyme Regis. The trunk is shaped 

 like that of a narrow skate of the family Rhinobatidse, and the 

 rosti'al spine in the male is long" and slender ; there is no dorsal 

 fin- spine. Another Jurassic family is that of the Myriacan- 

 thida?. Myriacanthus itself, also from the Lower Lias of Lyme 

 Regis, is represented by numerous fragmentary sjjecimens. 

 One slab of Af. gramdatus shows the dorsal and rostral sj^ines, 

 and a produced snout resembling that of the existing Gallo- 

 rhynchns. The dentition (originally named Progiiathodus) is 

 remarkable for a median chisel-like tooth in front of the lower 

 jaw. The long dorsal spine is covered with tubercles, which 

 are often pointed and thorn-shaped. The still-surviving family 

 of Chimseridfe is first represented by teeth of Ganodns and 



