78 



ANATOMY OF VERTEBEATES. 



03 



{Narcine), and at the same time with distinct pterygoid 



cartilages.' 



Four or five short cartilaginovis rays diverge from the posterior 

 mamin of the tympanic pedicle, ib. c, and support a membrane 

 answerincr to the opercular flap in Osseous fislies ; in their ultimate 

 homology these rays are the skeleton of the diverging appendage 

 or limb of the tympano-mandibular arch. 



The hyoid arch in Squatina, as in most other Plagiostomes, 

 consists of two long and strong cerato-hyals, and a median flat- 

 tened symmetrical piece, 

 the basi-hyal. Six short 

 cartilaginous rays extend 

 outwards from the back 

 part of the cornua, support- 

 ing the outer membranous 

 wall of the branchial sac : 

 these answer to the bran- 

 chiostegal raj's in osseous 

 fishes, and support the di- 

 verging appendage or limb 

 of the hyoidean arch. But 



^^Z'^'^^^Ib— r^-5^^5l?^^' ^^^'^ ^'^^^ '^^ integument in 



^ ■ '^ ^ ' — '"""^■'^ which they project is not 



liberated, and is continuous 

 with that supported by the 

 opercular rays from the 

 tympanic pedicle. Five 

 branchial arches, fig. 30, 

 I, 2, 3, 4, 5, succeed the 

 hyoidean ; but are sus- 

 pended, as in the Lam- 

 prey, I'rom the sides of the 

 anterior vertebra3 of the 

 trunk. In the Sea-hound 

 [Sri/uniiis iicliia), fig. 63, the 

 ceratobranchials, _/', f, and 

 basiln-anchials, c, e, are 

 shown, with the frame- 

 work of the gills, 17, /. Be- 

 hind these arches is the sca- 



]iulo-coracoid arc, 52, united by cartilaginous confluence at the 



mid-line, not by ligament as hi the Sturgeon. 



' xxi. I 8.')6, ])1. V. i\%%. 3 S: 4. It niay be questioned wliellief tlic ilctuclied pliite, 

 e.'i]k'(l |i:iliitii}c l)y J)r Ileiile, be not rather tile cntoiiteryjroul. 



Pliiil] Willi liraiicliial and scnpiilar arcliop. .9cf/»i 



