230 PAL.SONTOL0GY OF NEW-YORK. 



294. 3. ILL^NUS TRENTONENSIS. 



Pl. LX. Fig. 5. 

 Bumastis trentonensis. Emmons, Geol. Report, pag. 390, fig. 1. 



General form oval-ovate, very convex ; buckler semicirciilnr, rounded and ventricose in 

 front, elevated behind ; glaliella scared}' distinct, narrow in the middle, but expanding 

 before ; eyes approximate, large, form 1 facial suture making a deep and abrupt sinus at 

 the eyes, from whence it turns outward and backward ; central lobe of the thorax broad ; 

 segments plane, flat, continuing into the lateral lobes ; longitudinal furrows shallow, un- 

 defined, slightly continuing into the buckler, and less distinctly into the caudal shield ; 

 caudal shield sublriangular, very convex in the middle, and descending abruptly at the 

 sides, the margin slightly expanded. Surface marked by fine converging imbricating striae, 

 as in other specimens of the genus. 



This rare fossil was obtained by Dr. Emmons, from a boulder near Hogansburgh (N. Y.); 

 but from other associated fossils, it clearly belongs to the Trenton limestone. 



The original of the perfect specimen has been lost, and our description is taken from a 

 plaster cast. I have placed it under the Genus Illjenus, to which it properly belongs, the 

 distinctions between this genus and the Bumastis being scarcely decisive. 



295. 4. ILLiENUS LATIDORSATA (n. 5^.). 



Pl. LX. Figs. C a, b. 



General form broadly elliptical ; buckler convex, ventricose, thickened in front; thorax 

 with ten narrow articulations ; middle lobe of the thorax very broad ; lateral lobes narrow ; 

 surface marked by prominent imbricating lamellose striae. 



The specimen is a fragment, preserving five of the articulations very distinctly, and 

 fragments of five others in the stone. The buckler is crushed and broken, so that it cannot 

 be perfectly represented. The articulations arc very slender, those of the lateral lobes being 

 suddenly bent forward just outside of the longitudinal depression. The great width of the 

 central lobe (which is four times wider than the lateral lobe) , the well defined longitudinal 

 groove, and sudden bending forward of the articulations of the lateral lobes, are distin- 

 guishing features, and show it to be clearly distinct from the two preceding species. 



Fig. 6 a. The fragment, natural size. 



Fig. 6 b. Three of the articulations enlarged, showing the lamellose striae. 



Position find locality. In the Trenton limestone near Waterlown ( New- York ) . 



{Cnbinft nf Mr. .Alexandkr Fitch.) 



