TWO NEW ELAS MOB RANCH FISHES. 



233 



Genus Protospinax, nov. 



Snout short and obtusely rounded. Teeth small, compressed 

 to a sharp edge. Pectoral fins extending as far backwards as the 

 pelvic pair; dorsal fin-spines large, laterally compressed, and 

 smooth, the first inserted opposite the pelvic fins ; anal fin very 

 small, close to the elongate-ovoid caudal, which is not notched. 

 Shagreen dense and fine, none enlarged ; lateral line supported 

 by a series of calcified ringlets. 



Protospinax annectans, sp. n. (PI. I. figs. 2, 3.) 



Specific Characters. — Attaining a length of about a metre. 

 Length of cranium slightly less than one-fifth, length of caudal 

 fin about one-sixth of the total length. Teeth smooth and 

 lozenge-shaped, their sharp-edged crown sometimes with a 

 prominent middle point. Antero-posterior measurement of 

 pectoral fin about equal to the length of the cranium, and nearly 

 twice as great as the length of the pelvic basipterygium. Dorsal 

 fins about equal in size, the first arising slightly in advance of the 

 middle of the fish. 



Description of Type Specimen. — The fossil, which is shown of 

 one-sixth the natural size in PI. I, fig. 2, is very fragmentary, 

 but there are definite points of contact between the pieces of 

 rock in which it is contained, and most of it is preserved in 

 counterpart, so that its general shape and proportions are recog- 

 nisable. The head and trunk are seen directly from above, 

 while the greater part of the tail is exposed in side-view. The 

 edges of the head and fins are sharply outlined by fine dense 

 shagreen, while the distinctness of part of the margin of the 

 caudal region is due to fossilised muscle. The cranium is well 

 calcified in the usual small tesserae, and evidently not much 

 distorted. Its postorbital part is about as broad as long, and the 

 postorbital processes are small and slender. There is very little 

 constriction between the orbits, which are completely within the 

 hinder half of the cranium. The olfactory capsules form relatively 

 large rounded lateral prominences in the middle of the cranium. 

 The rostral part is short and wide, not tapering but nearly 

 truncated in front, and remarkable for the large size of the 

 elongated anterior fontanelle which extends backwards between 

 the olfactory capsules. There is no indication of a posterior 

 fontanelle in the cranial roof. The jaws are not seen, but there 

 appears to be a vague trace of the mandibular articulation on the 

 right side well behind the occiput. All the vertebras are crushed 

 and broken, but they show much secondary calcification round 

 the primary double-cone, and this seems to have been in concentric 

 laminae (on the tectospondylic plan). As in many other fossil 

 Elasmobranchs from the lithographic stone, the body-muscles are 

 well preserved; and it is clear that while in the abdominal region 

 each myotome corresponds with one vertebral centrum, in the 

 anterior part of the caudal region each myotome comprises two 



