48 



In the cabinet of the Albany Institute there are a 

 number of specimens of the A. Selenurus. One of 

 our models represents the natural mould made by 

 the animal in the rock; the other is an impression 

 taken from it, in order to exhibit the animal in a 

 more satisfactory manner. 



ASAPHUS LIMULURUS.* Green. Cast No. 16. 



Cauda longa, spina munita sicut in Limulo; costis 

 abdominis in spinis retrorsum flexis, desinentibus. 



It is very much to be regretted that the abdomen 

 and caudal end only of this remarkable Asaph have 

 hitherto been discovered; it is, however, exceedingly 

 gratifying that the fragment still remains in so per- 

 fect a state. It forms a part of the magnificent cabi- 

 net of organic remains belonging to J. P. Wetherill, 

 Esq., now deposited in the Academy of Natural 

 Sciences, of Philadelphia. 



Dr. J. J. Cohen discovered a small specimen of 

 this species at Lockport, New York, which he has 

 presented to the Athenaeum, in Baltimore. 



Eight articulations of the abdomen, and ten of the 

 tail, are all of this fine species that we have seen. 

 The ribs, or costal arches of the abdomen have a 

 deep furrow on their upper surface, commencing at 

 the middle lobe, and terminating near their free ex- 

 tremities; these extremities appear all detatched from 

 each other, and end in reflected points or spines, so as 



* From two Greek words, which signify " Limulus tailed." 



