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Show 528 MR. A. S WOODWARD ON [Dec. 7, imperfect fragments are already represented by 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 consideration was communicated by Dr. H. Riley to the Geological Society in 1833, and subsequently published, with one slight modification, in that Society's ' Transactions'l. 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 (7. 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 volume2. 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 polyspondylus ; but Riley's prior description necessitated the adoption of the generic title Squaloraja, though his withdrawal of' dolichoynatha' 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 Pristiophoridae, 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 18723, he pointed out that the uppermost rostral prolongation was a true spine, homologous with the frontal spiue of the male Chirnaeroid Ischyodus orthorhinus, 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 recently4 published an account of the structure of the vertebrae in great detail. 1 H. Riley, " On the Squaloraja," Trans. Geol. Soc. [2] vol. v. 1833, pp. 83- 88, pi. iv. 2 L. Agassiz, ' Rechercbes sur les Poissons Fossiles,' vol. iii. p. 379, pis. 42, 43. p >p - 3 W . Davies, " O n the Rostral Prolongations of Squaloraja polyspondula, Ag.," Geol. Mag. vol. ix. (1872) pp. 145-150, pi. iv. * 0. Hasse, " Einige seltene palaontologische Funde," Palffiontographica vol. xnri. (1885) p. 4, pi. i. figs. 2, 3. ° V ' |
