40 Description of a New Trilohite. 



Art. III. — Description of a New Trilohite ; by Jacob Green, 

 M. D, Prof, of Chemistry in the Jefferson Medical College, 

 Philadelphia. 



Asaphus Diurus — Green. 



Clypeo ? costis striatis, tuberculatis ; cauda bipartita ; corpore 

 depress©. 



The fragments of this Asaph which I have examined, consist 

 of nineteen articulations of the abdomen and tail. The costal 

 arches of the lateral lobes are very peculiar. They are marked 

 by a shallow groove, or impressed line on their upper surface, 

 studded on each side with quite a regular row of bead-like granu- 

 lations. On each division of the vertebral column, there is but a 

 single row of pustulations. The lunate caudal end is more ex- 

 panded than in the cognate species, the A. Selenuriis, and the 

 concave side of the cressent, is more regularly rounded ; the 

 whole animal is much more depressed, than that species, and 

 the lateral lobes are much wider in proportion to the middle lobe 

 of the back. 



There are two specimens of this fine species in the cabinet of 

 William Wagner, Esq., of Philadelphia, both of which were found 

 in Green County, Ohio, in the neighborhood of Xenia. The 

 largest which measures two inches long and two and a half inches 

 wide, is a plaster cast from a weather beaten natural mould ; the 

 other occurs in a grey, sparry, argillaceous limestone rock. It is 

 perhaps worthy of remark, that all the specimens of the Asaph, 

 with a lunate tail which I have noticed, were natural moulds, 

 made by the animal in the rock, the shell or body having disap- 

 peared. 



I was informed some time since, by Mr. Abraham Sager, of 

 New York, that he had discovered several fine specimens of an 

 Asaph with a lunate tail at the foot of the Helderberg mountains 

 near the Caves, in which the horns of crescent which forms the 

 caudal termination were remarkably elongated and perfect. As 

 the A. Selenurus is found at Glenn's falls and at Becroft's moun- 

 tain near the city of Hudson, is quite a different rock from that 

 which occurs at the Helderberg, and as this last formation seems 

 analogous to the one in which the Asaphus Diurus is found, it is 

 probable that Mr. Sager's species may be the one now described. 



I am indebted to the kindness of Mr. Wagner, for the opportu- 

 nity of making out this species. 



