Descriptions of New Species of Fossils. 71 



parallel to the margin ; the posterior margin has a narrower and less well- 

 defined band of striae ; remaining portion of head minutely punctate. 

 Thorax minutely punctate ; striate on the outer pleural portion on each side. 

 . Pygidium marked \>y strong lamellose striae, which have their origin near the 

 anterior lateral angles and diverge in different directions over the surface, 

 running subparallel to each other around the posterior side ; a row of punc- 

 tures occur between the striae near the margin ; surface otherwise finely 

 punctate. The removal of the test shows that the shell was very thin, and 

 covered on the inside with minute and coarse punctures or shallow depression. 

 The lower surface of the doublure is. striate. 



This species is allied to the group of Illaeni, described by Prof. Hall, from 

 the Niagara group of Wisconsin and Illinois ; especially to the species Illamus 

 insignia and 1. annatus. To lllamiis Trentonensis, it has many points 

 in common. As far as I can judge from the figures and descriptions, it is a 

 distinct species. 



Dimensions of specimens described. 



Total length 6f inches. 



Length of head 2 



Breadth of head 8 *' 



Distance between the eyes 2£ " 



Length of thorax 2 " 



Length of pygidiifm 2| " 



Breadth of pygidium. . B " 



Formations and localities. Black River Limstone, Buck's Quarry, Russia, 

 Herkimer Co., N. Y. ; Trenton Limestone, Plattsville, Wisconsin. 



iLLiENUS MlLLERI, Billings. 



Illoinns Milleri occurs in the same beds with /. indeterminatus, both in 

 New York and Wisconsin. Tt also occurs in the upper beds of the Trenton 

 Limestone at Trenton Fails. Perfect specimens show ten thoracic segments. 

 The original type specimens had but nine ; one was probably pushed beneath 

 the head, as in all other particulars, the species agrees with that from Canada, 

 where it occurs in the Black River and Trenton Limestones. 



ASAPHUS, Brongniart, 1822. 



ASAPHUS HOMALONOTOIDES n. Sp. 



Glabella elongate, pointed in front ; broadest at the anterior third. The 

 dorsal furrows and occipital furrow give a subquadrate form to the central 

 portion of the glabella similar to that in species of the genus Homalonotus. 

 The occipital segment is defined, back of the glabella, by a slight depression 

 which is more strongly marked behind the eyes. A pair of glabellar fur- 

 rows are indicated by shallow depressions between the eyes. 



Pygidpa, associated with specimens of the above glabella, have a subtrian- 

 gular outline, prominent axial lobe, marked convexity, anterior margin with a 

 distinct pleural groove, and a shallow depression between the external margin 

 and the outlined pleural lobes. The subtriangular form and strongly marked 

 axial lobe, relate the pygidia to the equally distinct associated glabellae. 



A large pygidium referable to this species, is three inches in length, by 

 three and one-half in breadth, at the anterior margin. 



Formation and locality. Trenton Limestone, two miles above Dunlith, 

 111., north of State Line monument. 



