528 MR. A. S. WOODWARD OX [Dec. 7, 



imperfect fragments are already represented b}' remains as complete 

 as can be expected in a fossil state ; and such remains being now 

 forthcoming in the case of the remarkable Selachian, Squaloraja 

 polyspondyla, it is proposed once more to bring this interesting 

 form before the notice of zoologists. 



The first scientific account of the genus and species under consi- 

 deration was communicated by Dr. H. Riley to the Geological 

 Society in 1833, and subsequently published, with one slight modi- 

 fication, in that Society's ' Transactions ' \ A fine specimen in 

 the Bristol Museum, displaying the head and vertebral column, with 

 obscure fragments of the appendicular skeleton, formed the subject 

 of this memoir, and notwithstanding the author's limited means of 

 comparison, he rightly recognized its affinities both with the true 

 Sharks and the Rays, and expressed the circumstance in its generic 

 name. Riley, however, misinterpreted the snout and rostral spine, 

 regarding these as jaws, and originally suggesting the specific name 

 of dolichognatha in allusion to their elongated shape ; but Agassiz 

 pointed out to him the error in time for correction in an appended 

 note (/. c. p. 85), and the distinguished author of the ' Poissons 

 Fossiles' again figured and described the specimen in one of the 

 later parts of his third volume^. Agassiz, indeed, was already 

 acquainted with portions of the vertebral column and dermal 

 tubercles of the fish, and had enumerated these in his preliminary 

 manuscript notes under the name of Spinacorhinus poh/spondylus ; 

 but Riley's prior description necessitated the adoption of the generic 

 title Squaloraja, though his withdrawal of ' dolichognatha ' allowed 

 the Agassizian specific name to be retained. 



But although Agassiz's extensive acquaintance with the Selachian 

 order enabled him to throw further light upon the Liassic genus, 

 and point out its remarkable resemblances to the Pristiophoridse, he 

 still failed to comprehend the precise nature of the curious snout, 

 and it was left to Mr. William Davies, of the British Museum, with 

 still more materials at his disposal, to offer a complete explanation. 

 In an important paper in the 'Geological Magazine' for April 1872^ 

 he pointed out that the uppermost rostral prolongation was a true 

 spine, homologous with the frontal spine of the male Chimseroid 

 Ischyodus ort/iorhinus, then made known by Sir Philip Egerton ; 

 and he further demonstrated the absence of the appendage in some 

 individuals, which were naturally regarded as females. Davies, 

 moreover, added some notes on the vertebral column, and Hasse has 

 more recently * published an account of the structure of the vertebrae 

 in great detail. 



' H. Eilev, "On the Squaloraja," Trans. Geol. Soc. [2] vol. v. 1833, pp. 83- 

 88, pi. iv. 



^ L. Agassiz, ' Recherches sur les Poissons Fossiles,' vol. iii. p. 379, pis. 42, 

 43. 



' W. Davies, " On the Eostral Prolongations of Squaloraja polyspondyla, 

 Ag.," Geo!. Mag. vol. ix. (1872) pp. 14.5-150, pi. iv. 



* 0. Hasse, " Einige seltene palaontologische Funde," Palseontographica, 

 vol. xrxi. (1886) p. 4, pi. i. figs. 2, 3. 



