42 NEW YORK STATE MUSEUM 



Genus BOTHRioLEPis Eichwald 



Definition. Premedian plate of head shield not notched in front ; post- 

 median small, not excluding the median occipital from the posterior 

 boundary of the orbit ; extralateral, if present, small and narrow. Posterior 

 commissural canal of head shield formed by a V-shaped groove, the apex 

 of which is situated on the median occipital, and the anterior termini in 

 about the center of the lateral plates. Anterior dorsomedian plate over- 

 lapping the antero-dorsolateral, but overlapped by the postero-dorsolateral 

 plate. Pectoral appendages at least as long as the armored trunk, seg- 

 mented into a distal and proximal portion, the latter being much larger than 

 the former, which is narrow and tapering ; marginal scutes of the proximal 

 portion meeting mesially, with a minute anconeal element only on the dorsal 

 aspect ; articular plates in contact for some distance above the external 

 marginal on the outer aspect ; marginal and central scutes of distal portion 

 more numerous than in Pterichthys. Tail naked ; two dorsal fins. 



A knowledge of the structure of this genus being indisjaensable for a 

 correct understanding of the group, it is not surprising that the magnifi- 

 cently preserved specimens of B. canadensis, from the Upper Devonic 

 of Quebec, should have invited the most searching investigation on the part 

 of palaeichthyologists. The Canadian material is certainly unrivaled for 

 exhibiting finer anatomical details, and but for the information so derived 

 it would be dif^cult to interpret the poorly preserved remains occurring 

 elsewhere in this country and in Europe. Bothriolepis is regarded as the 

 characteristic Asterolepid genus of the estuarine aspect of the Upper 

 Devonic, and is represented by four American, and some half dozen foreign 

 species in strata of that age. 



