158 PALEONTOLOGY OF NEW-YORK. 



201. 2. MODIOLOPSIS PARALLELA, 



Pl. XXXV. Fig. .5. 

 Cypricardites paralhla. Conrad in M.S. 



Subcyliiidrical ; sides nearly parallel ; hinge line extended ; imibones not prominent. 



I find the above figure among those of the Trenton limestone by Mr. Conrad, marked 

 Cypricardites parallela. Not Iiaving seen the original, I cannot give a full description. It is 

 evidently a species of Modiolopsis closely allied to the preceding one, but distinguished 

 liy its nearly parallel sides and greater extension of the hinge line. 



202. 3. MODIOLOPSIS FABA. 



Pl. XXXV. Figs. C «, h, c, tl. 

 J\ruculites faba, C0NR.4.D. Emmons, Geol. Report, 1S42, pag. 3'J5, fig. 5. 



Subelliptical or obliquely ovate, ventricose, witli a sinus extending from beak to base ; 

 umbones prominent, near the anterior extremity ; posterior side expanded, sometimes be- 

 coming alate, rounded at the extremity ; muscular impression close to the anterior margin ; 

 surface marl^cd by fine concentric lines, and sometimes a few imbricating lamellaj which 

 leave an impression upon the cast. 



This species is strongly marked l)y a depression, commencing at the beaks, and becoming 

 broader and deeper below, producing a conspicuous sinus in the base. This depressed line 

 from the beak sometimes appears to divide the two sides of the shell more equally than in 

 others, often leaving the sinus in the base near the centre. The beaks in some specimens, 

 both young and old, approximate towards the centre, giving the fossil a somewhat equi- 

 lateral aspect ; but these characters are deviations from the prevailing ones. It should he 

 observed, also, that the anterior lobe produced by this sinus is often compressed and 

 extended, giving an Avicula-like feature to the shell. 



Fig. 6 a. A large and characteristic form of this shell, the muscular impression visible at the anterior 



extremity. 

 Fig 6 A. A smaller specimen, less regularly rounded. 



Fig. 6 c. A specimen having a more oblique form, with the anterior lobe more compressed and extended. 

 Fig. 6 d. A young specimen, having the umbones and sinus nearly central. 



Position and locality. In the concretionary layers of the Trenton limestone at Watertown ; 

 in the black comjjact strata of the same rock at Sugar River (Lewis county), and in tiie 

 higher crystalline strata at Middleville. (*''«'<^ CoihcUon.) 



