108 



MEMOIRS OF THE CARNEGIE MUSEUM 



of various longitudinal, transverse and oblique ridges, especially within the areas of 

 the vertebral scutes, this part of the carapace being fairly smooth in the type. 



Fig. 1. Carapace of Baena arenosa Leidy. C. M. No. 2356. X H- '«., neural scute; v.s. 1-v.s. 5, 

 vertebral scutes one and five. 



In the measurements of the vertebral scutes it also differs from the type, but 

 agrees almost exactly with the type of Baena affinis Leidy, which is now regarded 

 by Hay, following Leidy and Cope, as being a synonym of B. arenosa. The verte- 

 bral areas of this type are also in accord with the present specimen. In order 

 to show the close agreement of the present individual with the above-mentioned 

 specimens a table giving the comparative measurements of the vertebral scutes 

 of each is herewith appended. 



Comparative Measurements of Vertebrals. 



Since the anterior portion of the carapace is missing in the type of the species 

 and in all subsequently discovered specimens the complete anterior margin in the 



