A. Smith Woodtcard — The Cretaceous Saiv-Fish. 633 



the trunk it makes some approximation to tbe Sqnatinid^, Ebino- 

 batidee, Pristiopboridse, and Pristidae. From tbe first family tbe fisb 

 is, of course, immediately distinguisbed by tbe production of tbe 

 snout ; and from tbe second family it is likewise separated by tbe 

 structure and armature of tbis rostrum. From tbe Pristiopboridee 

 it is distinguisbed by tbe forward production of tbe propterygium of 

 the pectoral fin, which would cause the gill-clefts to open on tbe 

 ventral aspect of the trunk, or at least direct them towards the 

 ventral aspect as much as in the existing Squatinid^ ; and there 

 are also important differences in the structure of tbe snout and tbe 

 paired fins, the latter in the Pristiopboridee always exhibiting a 

 great extension of skin beyond tbe cartilaginous rays, as in ordinary 

 sharks. From Prhtis, the type-genus of tbe Pristidge, the fish now 

 under discussion merely differs essentially (1) in the simple and 

 non-implanted character of the rostral teeth, (2) in the extension of 

 tbe median rostral cartilage to the end of the snout, and (3) in tbe 

 relatively short and broad form of the trunk, with the pectoral fins 

 almost reaching the pelvic pair. None of these characters, or any 

 of the minor points to be noted in tbe generic diagnosis of Schro- 

 rhjnchns, seem to justify its being placed in a family distinct from 

 that including Pristis ; and the present investigation therefore con- 

 firms former suspicions as to the systematic relationships of the fisb. 



If so much be admitted, it is evident that Sclerorhynclms remains 

 as the most generalized described form of the saw-fishes, and at 

 the same time their earliest known representative. It is, however, 

 difficult to understand how tbe curiously complex rostral teeth of 

 tbe typical Pristis can have been evolved, from an armature similar 

 to that of Sclerorhynchus ; and it is contrary to current belief to 

 suppose that the much elongated trunk of Pristis is not a primitive 

 inheritance from the sharks, but an indirect modification through 

 some almost skate-like form of trunk such as that of tbe Lebanon 

 fisb. So far as known, Propristis ^ appears to be an intermediate 

 link from the Lower Tertiary, tbe ordinary Pristis-Wke teeth in this 

 genus being described as not fixed in sockets in any secondarily 

 developed cartilage on the border of the pair of cartilages of the 

 rostrum. Nevertheless, it must at present suffice to record Sclero- 

 rhynchus as occupying an undetermined position in the family, 

 capable of definition, but awaiting tbe discovery of more Mesozoic 

 and early Tertiary genera to elucidate its precise significance. 



In conclusion, the following diagnoses may be appended : — 



Genus Sclerorhynchus. 

 [A. S. Woodward, Catal. Foss. Fishes, B.M., pt. i. 1889, p. 76.] 

 Body depressed ; pectoral fins relatively large, triangular, extend- 

 ing behind almost as far as tbe origin of the pelvic fins, and having 

 the propterygium much produced forwards. Kostrum gradually 

 expanding at tbe base, and supported throughout its length by the 

 median rostral cartilage of the cranium with one pair of lateral car- 

 tilages ; rostral teeth simple, loosely attached to tbe skin. Teeth in 

 1 "W. Dames, Sitzungsb. math.-phys. cl. k. preuss. Akad. Wiss. 1883, pt. i. p. 136. 



