BOTHRIOLEPIS. 



1 1 3 



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placed just at the " elbow" joint, whereby the external and internal marginals are 

 allowed to come together for a considerable 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 is, however, not seen in the Canadian specimens, though demonstrable 

 in many fragments from Scotland and Russia. 



The lower or " fore " arm is slender and pointed, and is constructed on the 

 same plan as in Asterolepis, only there are above and below two central pieces 

 (besides the terminal) and consequently there are three marginal elements (m.) on 

 each side. 



Postscript to Restoration of Bothriolepis. — Regarding the apparent absence of 

 a tail in otherwise complete examples of this genus I wrote in 1888 : 



" It is remarkable that no tail is seen in Bothriolepis, though numerous 



Fig. 59. 



Professor Patten's reconstruction of Bothriolepis seen from the side. From his paper quoted below. 



specimens both of B. Canadensis and B. hydrophilus seem perfect in every other 

 respect. It is therefore plain that caudal scales were absent, though it does not 

 seem to me quite so safe to assume that no caudal appendage was ever present, 

 for the posterior aspect of the carapace shows a large opening, just as in Pterichthys, 

 out of which it is difficult to conceive that absolutely no body prolongation ever 

 proceeded, and it does seem quite possible that a tail might have existed, though 

 unprovided with hard parts capable of preservation. Moreover, in a specimen of 

 B. Canadensis in the Edinburgh Museum there is to be seen, just at the place 

 where the tail occurs in Pterichthys, a peculiar dark organic-looking film, which is 

 strikingly suggestive of the remains of such an appendage." 



Since the preceding general account of Bothriolepis was in type I have received 

 a paper from Professor Patten, of Dartford College, New Hampshire (" New Facts 

 concerning Bothriolepis," 'Biol. Bulletin,' vol. vii, No. 2, July, 1904, pp. 113-124), 

 in which such a tail is in fact described and figured in B. Canadensis. It was 

 clearly composed of soft tissues, with the exception of a row of short slender rod- 



