530 MR. A. S. WOODWARD ON [DcC. 7, 



of the vertebral column. But the detached spines would appear to 

 afford evidence of two or more forms as yet unrecognized, and the 

 small example, no. VIII., is particularly distinct. It is very possible, 

 indeed, that when more specimens of the genus are available for 

 study, the characters of the rostral appendage will enter promi- 

 nently into the diagnosis of each species ; but I only venture, on 

 present evidence, to distinguish the possessor of the small spine no. 

 VIII. (Plate LV. fig. 6), and this may be appropriately designated 

 by the name of S. tenuispina. The fossil in question is separated 

 from its homologue in the known species by its much more slender 

 and acuminate shape, and possibly, though not certainly, by the 

 slight concavity of the proximal half of its upper surface. 



During the investigation of these fossils I have had the privilege 

 of discussing the subject with several zoological and palaeontological 

 friends, to whom I am indebted for some valuable suggestions noted 

 in the following pages. I desire especially to return thanks to Prof. 

 W. K. Parker, F.R.S., for much kind assistance in regard to the 

 skull ; to Mr. G. B. Howes, for a continuance of the help so freely 

 given on previous occasions ; to Mr. G. A. Boulenger, for the facili- 

 ties afforded in the study of the recent Selachians under his care ; 

 and to my senior colleague, Mr. William Davies, to whose earlier 

 work reference is so frequently made in the sequel. 



Anatomical Description. 



External Form. — Commencing the description with a brief notice 

 of the general external form of Squaloraja, attention may be first 

 directed to the beautiful specimen no. I., represented in Plate LV. 

 fig. 1. As the shape of the head had already led Agassiz and Davies 

 to suspect, the proportions are found to be very similar to those of 

 the living Pristiophoriis. Assuming that about three centimetres 

 are missing from the tail of the specimen, the snout will have 

 occupied one quarter of the entire length of the animal. The body 

 must have been but slightly compressed from above downwards, and 

 the pectoral fins were undoubtedly free, having no connection with 

 the head ; the shoulder-girdle, however, is placed relatively nearer 

 to the chondrocranium than is the case either in Pristiophorus or 

 Pristis, though appearances are not improbably deceptive, owing to 

 crushing during fossilization. It is impossible, of course, to deter- 

 mine whether the gill-openings were ventral or lateral, and scarcely 

 any traces of the branchial arches have been preserved. The 

 pectoral fins, as usual, are much larger than the ventrals, and the 

 tail is long and slender, without spine, as admirably shown in no. III. 

 (fig. 7). Unfortunately, all sure indications of dorsal and caudal 

 fins are wanting, though it is scarcely likely that these appendages 

 were absent in the living fish. 



Dermal Structures^. — In regard to the integument and its appen- 

 dages, the new fossils afford some interesting additional information. 

 No less than eight rostral spines are now available for study ; and 



' The dentition will be more conveniently treated in a later section, p. 534, 



