148 Silurian Fossils of Nova Scotia. 



11. MODIOLOPSIS ? RHOMBOIDEA. N. Sp. Fig. 6. 



Shell sub-rhomboid, rounded in front, wider and obliquely trun- 

 cate behind, hinge-line slightly ascending from the anterior end ; 

 beaks subterminal, posterior umbonial slope obtusely subangular 

 below, anterior to which the shell is flattened ; basal margin nearly 

 straight, the shell gradually widening behind and the posterior 

 basal extremity abruptly rounded. Surface evenly striated con- 

 centrically. 



Anterior muscular impression very strong, posterior muscular 

 impression less strongly defined, but still very conspicuous and 

 sub-duplicate ; palleal line simple, nearly parallel to the basal 

 margin, strongly and almost equally defined in all parts of its 

 length between the two muscular imprints. 



This shell bears some resemblance to M . primiffenius, but is less 

 ventricose in tlie middle, and the sub-angular umbonial slope ia 

 not so well defined in that species. 



12. MODIOLOPSIS SUB-NASUTUS. N. Sp. 



Shell elongate sub-spatulate, tlie length being more than twice 

 "the greatest width hinge-line ; sliglitly ascending posteriorly ; 

 beaks sub-anterior, the anterior end very narrow, gibbous on the 

 umbones, with a sub-angular ridge on the umbonial slope which 

 extends to the postero-basal angle ; basal margin nearly straight, 

 the posterior end somewhat flattened and obliquely sub-truncate 

 at the extremity ; surface marked by concentric lines of growth. 



This shell bears a close general resemblance to M. nasutus of 

 the Trenton limestone, but a careful comparison shows it to be 

 wider and more abrupt at its posterior termination, while the 

 direction of the striae of growth is very distinctive, these marks 

 being regularly curving toward the posterior end in M. nasutus, 

 while in this species they are abruptly bent at the postero-basal 

 angle, and again on the cardinal side, corresponding with the 

 truncate posterior extremity of the shell. 



13. Clidophorus cuneatus. N. sp. 



Shell ovoid, gibbous in the middle and on the umbones, gra- 

 dually declining behind ; beaks anterior, sub-terminal ; anterior 

 •end broadly rounded, the posterior end narrower and sub-acute, 

 posterior umbonial slope marked by an obtuse rounded ridge, 

 (which extends to the posterior extremity, and below this an unde- 



