218 PALEONTOLOGY OF NEW YORK. 



of their sculpture which consists of fine incised lines separated by broad, re- 

 trallv sloping annulations. This ornamentation is noticeably coarser than in 

 any of the associated species. 



Their size varies from a length and width of 4 mm. to a length of 6 mm. 

 and a width of 5 mm. 



Distribution. Hamilton group Centerficld and Canandaigua, Ontario county. 



TlJRRILEPAS NITIDULUS, 11. Sp. 

 PLATE XXXVI, FIG. 4. 



A single plate wanting the nuclear portion is distinguished from the asso- 

 ciated forms by its very line and closely set concentric striae, and its broad 

 posterior area, which is covered with conspicuous pits or punctoe, apparently 

 arranged also in concentric lines. The basal margin is gently sinuous, corres- 

 ponding with the sinuous concentric lines, and a broad low sinus is apparent 

 over the median portion of the valve. 



The length of the specimen is 2.5 mm., and the height about 2 mm. 



Distribution. Hamilton group. In the lower shales at Fall Brook, Hopewell, 

 Ontario county. 



TlJRRILEPAS FOLIATUS, 11. Sp. 

 PLATE XXXVI, FIG. 15. 



A single plate has an elongate semi-lanceolate or semi-saggitate outline, and 

 a length equal to three times the height. The nucleus is not distinctly seen in 

 the specimen, and the concentric lines in its vicinity appear to be obsolete, but 

 further downward are closely crowded and clearly defined. The posterior 

 margin is long and straight, appears to have been slightly elevated or thickened 

 and possibly folded. The anterior margin seems to have been abrupty curved 

 across the plate, rounding backward to the straight basal margin. 



The height of the plate is 2.5 mm., its length 7 mm., and the distance along 

 the posterior margin 9 mm. 



Distribution. Hamilton group. In the limestone layers at the base of the 

 Hamilton shales: Canandaigua, Ontario county. 



