90 



singular trilobite remains, and it is doubtful whether 

 what is said to be the punctured fillet, " nearly 

 straight in front of the middle lobe," be not the com- 

 mencement of the articulations of the abdomen. The 

 whole fragment looks very much like the head of 

 some large Asaph or Ogygia. 



GENUS BRONGNIATIA. Eaton. 



Professor Eaton has proposed the name Brongnia- 

 tia (Brongniartia?) for a genus of trilobites, which 

 we think he has not defined with sufficient accuracy 

 to be of any practical use. The Isotelus gigas of 

 Dr. Dekay, which has been for a long time so well 

 established, is here ranked merely as a species under 

 the name of B. isotela. The relic which we described 

 before the Geological Text Book appeared as the 

 Triarthrus JBeckii, forms the species B. carcinoclea 

 and the trilobite which is supposed to be the Asaphus 

 platycephalus of Stokes, is the only other species 

 mentioned. The A. platycephalus,* we know to be 

 identical with the I. gigas, and as the animal remain 

 described by Mr. Eaton is entirely different from Dr. 

 Dekay's fine species, we subjoin the account given in 

 the " Text Book." 



Genus Brongniatia Fore abdomen always, and 

 post abdomen in some cases, longitudinally divided 

 into three lobes, by regular series of undulations tra- 



* For a figure and description of the Asaphus Platycephalus, 

 by Mr. Stokes, see Transactions of the Geological Society. Se- 

 cond Series, vol. i. 



