88 



IOWA GEOLOGICAL SURVEY 



Fig. 12. Fig. 13. 



Fig. 12. Bothriolepis canadensis Whiteaves. Upper Devonian; Scaumenac Bay, Province of Quebec. 

 Restoration of dorsal aspect, x § (alter Traquair). 



£z- m. occ, median occipital; I. occ, lateral occipital; ag., angular; pt. m., post-median; p. m., pre-median; 

 I., lateral; e. I., extra-lateral; m., median; o., ocular; a. d. I., 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., dor- 

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

 lower arm; t., terminal. 



Fig. 13. The same from the ventral aspect, xs (after Traquair). mx., maxillary plate; s. /., semilunar; 

 a. v. I., anterior ventro-lateral; p. v. I., posterior ventro-lateral; m. v., median ventral; car., ventral artic- 

 ular; -v. a., ventral anconeal; c, centrals; m., marginals of lower arm; £., terminal. 



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 arrange- 

 ment, save that the dorsal anconeal (d. a.) is a smaller rounded 

 element placed just at the " elbow" joint, whereby the external 

 and internal marginals are allowed to come together for a con- 

 siderable distance between it and the distal extremity of the 

 dorsal articular (d. ar.). The two articulars, as noted in the 

 generic diagnosis, meet together on the outer aspect over the 

 external marginal; this relation, however, is not always clearly 

 visible in the Canadian specimens, though demonstrable in many 

 fragments from Scotland and Eussia. The lower or "fore" 

 arm is slender and pointed, serrated along the external and in- 

 ternal margins, and composed of a greater number of pieces 

 than in Pterichthys or Asterolepis. 





