828 PROfEEDTXas OF THE NATTOXAL MFSEUM. vol. xxviii. 



OBOLUS TETONENSIS NINUS, new variety. 



This variet}^ differs t'l'om the })ar(nit species and from (/. inathialis 

 by the more elongate form of the dorsal valve and the more acuminate 

 form of the ventral valve, the cardinal slopes of the latter extending 

 much further forward in the variety ninas than in the two species. 



The advanced ]K)sition of tlie visceral area in the ventral valve may 

 he compai'ed with the visceral area of Ohohis (L.) crax^ux. 



Fornuitlon <iud locality. — Middle Cam])rian. Reagan formation, 

 one-half mile east of Canyon Creek, 15 miles northwest of Fort Sill, 

 Oklahoma Territor}-; also on west side of Honey Creek, near SE. 

 corner, sec. 86, T. 1 S., R. 1 E. NE. i sec. 2, T. 2 S., R. 1 E. Ard- 

 more map, (ireological Survey, Indian Territory. 



OBOLUS PHERES, new species. 



Tliis is one of the smallest of the Oholus species known to me. It 

 recalls at first sight 0. (Z.) 'wino/ta conve.tus,' but it dilfers in having 

 a thick, lamellated shell, and in being more rounded on the cardinal 

 angles. The exterior surface is marked by concentric lines of growth. 

 The shell is built up of thin layers or lamelhe, those toward the front 

 and sides being arranged obliquely to the surface, as in all of the 

 thick-shelled species of Ohohix. 



Forniatloh and locality. — Uppei- Cambrian. Argillaceous shales, 

 interbedded in sandstone at Fox Glen, 8 miles east of Baraboo, 

 Wisconsin. 



OBOLUS (LINGULELLA) CHINENSIS, new species. 



General form ])roadly subovate with the ventral valve broadly sub- 

 acuminate and the dorsal valve oval with the postero-lateral slopes 

 somewhat straightened. There is some variation in the proportions 

 of width and length in different shells. Valves rather strongly convex 

 for so thin a shell, in this respect resembling species of Dicellohius. 

 Surface marked by tine concentric stri^ and lines of growth and very 

 fine undulating concentric lines; this outer surface is usually a dull 

 black and adheres to the matrix; when the outer layer is exfoliated 

 the surface is shin}'^ black and marked by numerous radiating striss in 

 addition to concentric strite; the inner surface shows a few scattered 

 punctte in addition to radiating and concentric stri{« outside the vis- 

 ceral area. The shell is of medium thickness and formed of a thin 

 outer layer and several inner layers or lamellae that are slightly oblique 

 to the outer la3^er; the lamella? are more numerous and more oblique 

 to the outer layer over the anterior and antero-lateral portions of the 

 shell. The ventral valves average 3 mm. in length, with width vary- 

 ing from 2 nmi. to 2.6 mm. The dorsal valve is slightly shorter than 

 the ventral when the two valves have the same width. 



