130 NEW YORK STATE MUSEUM 



by Patten (The Vertebrates and Their Kin) is a creature 2 to 3 inches 

 long, with a short semicircular head, a broad thorax or mesosoma of 

 six segments, followed by three narrow segments of the postabdomen 

 with a long single telson spine. The head is marked by five curved 

 radial furrows diverging on each side from the central subtriangular 

 glabellar elevation; and these divide the surface into corresponding 

 radial ridges. Doctor Patten has called attention to the retention 

 of this primitive structure in the Limulus embryo, a fact which' 

 certainly seems to bespeak the direct descent of the latter from this 

 ancient primitive merostome. 



The New York fossil, which is here designated by the generic name 

 Bunaia, is like Bunodes in these cephalic structures. Though of 

 very much smaller habit, the carapace shows on the upper surface 

 the same arrangement of parts and on the underside this pentameral 

 division is clearly accompanied by remains of the five pairs of legs, 

 the mouth orifice and, as it seems, the chelate first legs folded down 

 close alongside the mouth. 



We illustrate here in connection with these features a head of 

 Bunodes lunula, the Oesel species, showing a similar arrange- 

 ment of the five pairs of legs and in addition what appear to be the 

 lateral thickenings of the glabellar ridges. This is a State Museum 

 specimen from which the very thin epidermal film has been removed. 

 Further, the head shield of Bunaia is progressed over that of Bunodes 

 in its thickened margins and extended cheek spines. Patten believed 

 that antennae were present in Bunodes and so restored it, but we 

 find no evidence of these structures in Bunaia. 



In our specimens the chief difference of Bunaia from Bunodes is 

 in the structure of the abdomen. In the latter there are six broad 

 segments followed behind by three narrow ones. In Bunaia this 

 structure appears to be somewhat different. The cephalon or head 

 shield is followed behind by narrow segments of which seven or eight 

 can be counted, with possibly one missing. These seem to be of 

 somewhat unequal length and to be longitudinally ridged but without 

 lateral flanges. Our knowledge of this structure is restricted to a 

 single example and is subject to qualification. In one of the three 

 specimens there is a broad, detached, smooth spine lying alongside 

 the head, which may have been the telson, though apparently pretty 

 large for the species. 



The size is as follows: width of carapace 8 mm; estimated total 

 length of animal, inclusive of telson, 23 mm. 



Remarks. The distinctions we have pointed out are sufficient to 

 justify the generic division Bunaia, but there are still some points 



