66 



BRITISH FOSSILS. 



knowledge of several other associated forms. Through the kind- 

 ness of Mr. Powrie, the Kev. Hugh Mitchell, and the Rev. Henry 

 Brewster, I have been enabled to examine the most perfect speci- 

 mens hitherto discovered, and from these materials the following 

 description of Climatus scutiger is derived. The specimens comprise 

 two forms, the one of more slender proportions than the other. In 

 the absence of more important differential features, it would be 

 impolitic to attach specific value to a discrepancy of this kind ; it 

 may be due to casual or local influences, or be a sexual character. 

 It suffices for the present to notice the fact, leaving the question of 

 specific value to be settled by future investigation. The specimens 

 range from one inch and a half to two inches in length, from 

 the snout to the base of the tail. The latter organ is rarely pre- 

 served entire, in consequence of its extreme tenuity and delicate 

 structure, and the fragile texture of the shale in which the specimens 

 are imbedded ; but I am informed by Mr. Powrie, who had the 

 advantage of seeing the specimens when first uncovered, that the 

 upper lobe of the tail measures about one-third of the total length 

 of the fish. This measurement would give about three inches as 

 the extreme length of a full grown individual. The form and pro- 

 portions of the head closely resemble those of the head of Acan- 

 tJiodes. As in that genus, the surface of the cranial bones is richly 

 chased, but the sculpturing, instead of being continuous in ver- 

 micular gyrations, is more isolated, so as to give the appearance of 

 a repetition rather than a continuation of the pattern. The fins 

 are all supported by strong conical spines, or rather spurs. They 

 correspond in number with those of Diplacanthus, namely, two 

 pectoral, two ventral, two dorsal, and one anal. They are all 

 grooved longitudinally, the ridges between the grooves being 

 slightly crenulated, as in Ctenacanthns. A few transverse lines 

 (indicating, perhaps, periods of growth) occur near the base of the 

 spines, crossing the longitudinal pattern, and causing the reticulate 

 character which suggested the specific designation for the Balrud- 

 dery spine described by Professor Agassiz. The pectoral spines are 

 nearly as broad as long, short, and recurved. They are so firmly 

 attached to strong coracoids that the latter appear to be integral 

 portions of the base of the spines. The pectoral spines are easily 

 distinguished from the other fin spines by the arrangement of the 

 superficial pattern. In these the ridges run parallel with the 

 posterior margin, whereas in the dorsal and anal fins they coincide 

 with the anterior curve of the spine. The ventral spines are small ; 

 they are situated far back, in close proximity to the anal fin. The 



