57 



sides of the body, and forms a sort of hem; below 

 the central portion of the tail it makes a short acute 

 projection, which seems to be supported by a short 

 costal elongation of the middle lobe. Length two 

 inches and a half. 



The A. Micrurus was found in the black foetid 

 limestone of Trenton Falls, by M. H. Webster, Esq., 

 and by him placed in the rich collection of trilobites 

 in the Albany Institute. The limestone in which 

 this Asaph is embedded, is almost one entire mass of 

 petrifactions. The general aspect of the A. Micru- 

 rus is very similar to that of a calymene but judg- 

 ing from its structure, it could never contract its 

 shell into a spherical figure. Its minute tail, and 

 narrow membranaceous expansion round the terminal 

 edges of the lateral lobes are quite peculiar, and de- 

 termine it to be an Asaph. 



ASAPHUS WETHERILLI.* Green. Cast No. 20. 



Clypeo postice arcuato, sulcato; abdominis articu- 

 lis duodecim; cauda vix membranacea; cute corea- 

 cea vix punctata. 



The contour of this beautiful Asaph is very regu- 

 larly ovate; unlike most of the remains of this genus, 

 the buckler is still attached to the abdomen, though 



* I have named this species in compliment to my friend, John 

 P. Wetherill, Esq., whose magnificent cabinet of fossils in the 

 Academy of Natural Sciences of Philadelphia, will ever remain 

 as a monument of his discrimination, enterprise, and liberality. 



