15 



There are nine outwardly directed serrations in a space of 3 mm. A similar ridge likewise 

 occurs on the posterior border with slightly larger serrations, about six of the latter occurring 

 in a space of 3 mm. These posterior serrations show a tendency to point backward, and they 

 are not continued so far toward the base of the spine as are those of the anterior border. 

 The measurements of this specimen are as follows : — length (distal half missing) 13 mm., 

 greatest height at proximal end 6 mm., antero-posterior diameter at broken distal end about 

 2'8 mm., with a vertical diameter distally of about 1-6 mm. The pectoral spines in the col- 

 lection are of various sizes, from 4 up to 16 mm., as measured in a vertical direction across 

 the base, with the more anterior part in proportion. 



The serrations in the majority of the specimens have been worn down, and in some cases 

 almost entirely removed, although indications of them can' still be seen. In the largest 

 specimen (16 mm. across the base) the number of serrations in a space of 3 mm. is about six 

 on both borders. In all, the ornamentation of the sides is the same. 



A few dorsal fin spines, with sculpture similar to that of the pectoral spines, are, probably, 

 also referable to this species. They are broken across at some distance from the base, and 

 the distal end lost. One, of small size and somewhat worn, is serrated on both borders. In 

 a second, a large spine, figs. 14, 15 and 16, the anterior border is rugose, and no satisfactory 

 evidence of serrations can be made out; posteriorly its surface is deeply grooved proximally 

 as in the smaller spine, and the specimen is broken off behind where the serrations would 

 probably begin. The measurements of this large spine are — length of specimen 30 mm., 

 breadth across proximal end 18 mm., antero-posterior diameter at fractured distal end 8 mm. 

 transverse diameter distally 6'5 mm. 



A number of fragments from the distal end of spines are, probably, also referable here 

 The}' are longitudinally striated, and three are serrated on both borders. Another is serrated 

 at least on the posterior border ; whilst one bears on its posterior border comparatively long 

 backwardly curved barb-like denticles (figure 13). 



These spines appear to approach closely, in detail of ornamentation and shape, to those of 

 S. arcuatus, described by Cope from the Bridger Eocene of Wyoming. In the Oligocene 

 specimens the serrations of the borders, and the ornamentation generally, are on a smaller 

 scale. 



Amiurus cancellatus, Cope. 



Amiurus cancellatus, Cope, 1891. The species from the Oligocene or Lower .Miocene beds 

 of the Cypress hills. Geol. Survey of Canada, Contr. to Can. Palaeont., vol. Ill (quarto), 

 pt. I, p. 3, pi. I, figs. 4, ia-b. 5, ha-b. 



This species, founded on two vertebral centra from the Cypress hills, is one of two species 

 of the genus described from this region. 



In the 1904 collection are a few centra, with parts of others, that, judging from their 

 form and structure in comparison with the type specimens, are apparently referable to Cope's 

 species. 



In the type specimens the dense tissue of the articular surfaces is succeeded within by 

 vertical laminae forming two thin layers which are connected by tissue, disposed for the most 

 part longitudinally, in which are many openings of variable size having their longer axes in 



