56 



Two specimens of this Asaph are in the cabinet of 

 the Albany Institute, The one from which our cast 

 is taken, was found on the Helclerberg mountains; it 

 is embedded in a light grey coloured limestone shale* 

 The other specimen, which is much smaller, was dis- 

 covered near the Genessee river, in the State of New 

 York. The rock in which it occurs is identical in 

 its constitution with the other. It contains other 

 species of trilobites, and a number of shells. 



ASAPHUS MICRURUS.* Cast No. 19. Fig. 3. 



Cauda attenuata, acuta; corpore valde convexoj 

 costis striatisj parte marginal! vix membranacea. 



This fine, large caudal termination of an Asaph is 

 in the cabinet of the Albany Institute and it is a 

 subject of great regret, that all that has yet been dis- 

 covered relating to this highly interesting trilobite, 

 is to be seen in this fragment. 



There are eighteen articulations of the tail and 

 abdomen, which cannot be distinguished from each 

 other. The middle lobe is composed of a series of 

 straight, distinct, parallel articulations, very convex 

 about the middle, so as to form a kind of longitudinal 

 ridge down the back. The costal arches of the 

 lateral lobes are very distinct, and are longitudinally 

 striated or grooved on their upper surface, particular- 

 ly those near the upper part of the animal. The 

 membranaceous expansion is very narrow along the 



* From the Greek, for " minute tail." 



