

We annex, from Prof. Green, a notice, just received, Dec. 26, 

 1832, of a new trilobite. 



Asaphus Myrmecoides. — Corpore depresso ; costis latis, convexis, 

 tuberculis magnis ; cauda rotunda ? 



The large fragment, by means of which this species has been 

 identified, is in a fine state of preservation. Thirteen costal arches 

 and fourteen joints of the middle lobe, with two or three faintly 

 marked articulations near its extremity, can be very satisfactorily 

 made out. The costal arches are, therefore, more numerous than 

 the vertebral joints ; an organization not very uncommon with the 

 Asaphs. The first eight ribs and vertebrae, as seen in this fragment, 

 appear to have been articulated together ; after which this irregular 

 structure commences. The costal arches are rounded on their up- 

 per surface, without striae ; broadest near their lateral extremities, 

 and are, most of them, irregularly nodulous; these nodules re- 

 semble very much the protuberances on the ribs of the Pecten no- 

 dosus. The joints of the middle lobe are also rounded and nodu- 

 lous, but on these the nodules are disposed in the form of two very 

 obtuse paralellograms. What renders this fragment peculiarly inter- 

 esting, is that the lower portion of the upper shell, along one of the 

 lateral edges near the tail, is so fractured as to present the structure 

 beneath the ends of the ribs which have here scaled off. At first 

 sight the broad smooth edging round this part of the fossil, resem- 

 bles very much the membranaceous expansion beyond the lateral 

 lobes which is one of Professor Brongniart's generic characters of 

 the Asaph. This border indeed is very like the hem so strikingly 

 exhibited in the Asa'phus micrurus ; but upon comparing the ribs 

 on the opposite side, where they are perfect, with those terminated 

 by the border, it will be seen that they are much longer; what there- 

 fore, seems to be an expansion beyond the ends of the ribs in that 

 place, must be occasioned by the reflection of the shell beneath the 

 posterior portions of the lateral lobe. The inferior structure and 

 mechanism of this part of the fossil trilobite is thus, we believe, for 

 the first time developed. In a fine group of the Dudley fossils de- 

 posited in the cabinet of the Geological Society of Pennsylvania, a 

 similar inferior reflected edge may be seen beneath the buckler of tht3 

 Asnphus Debuchii. It is not uncommon in many of the recent 

 Crustacea, and, is strikingly exhibited along the lower edge of the 

 Limulus polyphemvs. 



