420 MEMOIRS OF THE CARNEGIE MUSEUM. 



teeth are given in the accompanying illustration (Fig. 7.) This peculiar differ- 

 entiation of the dentition in Asthenocormus is most nearly approached among 

 kindred forms by the Cretaceous Protosphyrcena, in which the more anteriorly 

 placed teeth are especially large, much compressed, and implanted in deep sockets. 

 In respect to various characters, the genera P achy cor mus, Hypsocormus, Astheno- 

 cormus and Protosphyrcena represent, in the order named, successive stages of 

 modification, at the same time closely mimicking in general form of body the 

 Tertiary Xiphiida? or "sword-fishes." 



Family ASPIDORHYNCHID^. 

 Genus Aspidorhynchus Agassiz. 



In this genus, according to Dr. A. S. Woodward, the vertebral centra are 

 always in the form of delicate rings, each bearing its own arch. The ribs are very 

 short and thin. In the abdominal region the neural spines appear to be separate 

 from their supporting arches, though this is not quite certain; in the caudal region, 

 both haemal and neural spines are fused with their arches, and the latter with 

 their respective centra. As might be expected from the stout proportions of the 

 rays, the supports for the dorsal and anal fins are especially robust; and they are 

 shown to be more numerous than the vertebral segments beneath them. The 

 scales are all thick and rhombic, strengthened by a slight internal median rib, 

 and those of the flank united by a large peg-and-socket articulation. The lateral 

 line pierces each scale it traverses.^'' 



41. Aspidorhynchus acutirostris (Blainville) . (Plate LXIV, fig. 3.) 

 (For synonymy cf. A. 8. Woodward, I. c, Pt. Ill, p. 419.) 



This species is represented in the collections of the Carnegie Museum by a 

 number of fine examples, certain of which are to be seen on exhibition in the Hall 

 of Fossil Vertebrates. The complete suite of specimens is cataloged as follows: 

 12, 14, 4741, 4743, 4774, 4745, 4746, 4777 + 4777a, 4779, 4810, 4823, 4814, 4864, 

 4867, 4868 + 4868a. 



Genus Belonostomus Agassiz. 

 42. Belonostomus muensteri Agassiz. (Plate LX, fig. 1.) 

 (For synonymy cf. A. S. Woodward, I. c, Pt. Ill, pp. 429-30.) 

 This species is represented in the collection of the Carnegie Museum by the 

 following examples: Cat. Nos. 4115, 4795, 4796, 4850, 4865, 4866. 



"For a description of the cranial osteology and other interesting details of the structure of two 

 species of Aspidorhynchus reference may be made to Assmann's paper "Ueber Aspidorhynchus" in 

 Archivfiir Biontologie 1906, Bd. I, Heft 1, pp. 49-80. 



I 



