36 



FISH GALLERY, 



Tope. 



Hammer- 

 head 

 Shark. 



Group B 



of 

 Squali. 



Spina- 

 cidse. 



Wall-case 17 is a fairly large specimen of Galeocerdo rayneri (1127) 

 from the Indian Ocean, also the jaws of another specimen (1126). 



The Tope, Galeus canis, 64, is a fish not uncommon on the 

 British coasts, and widely distributed in tropical and temperate 

 seas. It is a bottom-feeder, with a fairly long snout ; the spiracle 

 is minute, and there is no pit at the root of the tail. The jaws of 

 the Tope are exhibited (66) and the calcified parts of the vertebral 

 centra showing the cruciform pattern of the secondary calcification 

 (65). The Smooth Hound, Mustelus vulgaris, 68, differs from 

 the Tope in having closely set, flattened teeth, arranged like a 

 pavement (see jaws 69). It is a fish commonly found in British 

 seas ; the species Mustelus laevis is occasionally met with also, but 

 it has a more southern distribution than Mustelus vulgaris. 



The Hammer-head Shark, Zygoma malleus, is a strange-looking 

 Shark in which the anterior part of the head is broad, flattened, 

 and laterally elongated ; the eyes are situated at the extremities of 

 the lobes, and the nostrils occur just beneath the front edge ; the 

 spiracle is absent ; the teeth are similar in the upper and lower 

 jaws, they are oblique and have a posterior notch and margins 

 smooth or serrated. The Hammer-head Sharks are found in most 

 temperate and tropical seas. The specimen 71 on the floor of 

 Wall-case 2 is a small one ; a larger example (1129) hangs from 

 the rail opposite Wall-case 16 ; the jaws of a Hammer-head (1128) 

 are shown near the latter specimen. 



In the fishes of Group B of the suborder Squali the spiracles 

 are large, and the anal fin wanting. The line of the closed mouth 

 is nearly straight, and not crescentic as is so commonly the case 

 in the fishes of Group A. The calcification of the vertebral centra 

 either takes the form of primitive hollow double-cones immediately 

 surrounding the remnants of the notochord, or there are concentric 

 secondary laminae in addition. This group includes the families 

 Spinacidae, Petalodontidae, Pristodontidae, Rhinidse and Pristio- 

 phoridae. 



The family Spinacidae includes fishes, some of which, like 

 Spinax, 79, and Acanthias, 75, are slender and shapely, while 

 others, such as Centrina, 83, and Echinorhinus, 86, are bulky and 

 clumsy in appearance. The dorsal fins are provided with spines in 

 some genera (e. g. Centrina, Acanthias) , but not in others (e. g. 

 Scymnus, Echinorhinus) . The body is rounded or triangular in- 



