112 



OLD RED SANDSTONE FISHES. 



forwards and outwards, they pass over the lateral plates and terminate near the 

 flexure of the great groove close behind the origin of its small outer branch. It 

 may be noted that, as pointed out by Smith Woodward, a small sensory groove is 

 also seen on each maxillary plate. 



The articulations of the body-plates are as in Pterichthys, the anterior median 

 dorsal (a. m. d.) overlapping the anterior dorso-lateral (a. d. I.) of each side, but 

 being itself overlapped by the posterior dorso-laterals (p. d. I.). On the other 

 surface (Fig. 58) the place of the two semilunars of Pterichthys and Asterolepis 

 is apparently taken by a single plate (s. /.). The course of the lateral line groove 



Fig. 57. 



Fig. 58. 



Fig. 57. — Restored figure of Bothriolepis Canadensis; dorsal surface, m. occ, median occipital ; 

 I. occ, lateral occipital ; ag., angular ; pt. m., post-median ; p. m., pre-median ; I., lateral ; e.l., extra- 

 lateral; m., median; o., ocular; a. d. 1., anterior dorso-lateral ; a. m. d., anterior median dorsal; p. d. I., 

 posterior dorso-lateral ; p. m. d., posterior median dorsal ; d. a., dorsal anconeal ; d!. ar., dorsal articular; 

 e. m., external marginal; i. m., internal marginal; c, centrals of lower arm; jr., marginals of lower 

 arm ; t., terminal. 



Fig. 58. — Restored figure of Bothriolepis Canadensis; ventral surface, mx., maxillary plate ; s.l., 

 semilunar ; a. v. L, anterior ventro-lateral ; p. v. I., posterior ventro-lateral ; in. v., median ventral ; v. ar., 

 ventral articular ; v. a., ventral anconeal ; c, centrals ; m., marginals of lower arm ; t., terminal. 



is exactly as in Pterichthys, and, as already mentioned, its passage from the 

 external occipital of the head on to the anterior dorso-lateral of the body is in 

 many specimens distinctly verifiable. 



The pectoral appendages are longer than the dorsal aspect of the carapace, 

 and even pass beyond the termination of the ventral surface. The proximal portion 

 is also longer than the distal, though the proportion seems to vary ; roughly 

 speaking, however, the difference between the two portions is less than one third 

 of the longer. The proximal portion is, like that of Asterolepis, trigonal in 

 transverse section ; and the plates of which it is composed are also similar in number 

 and arrangement save that the dorsal anconeal (d. a.) is a small rounded element 



