56 BULLETIN OF THE LABORATORIES 



peculiarly liable to distortion. The species is normally somewhat 

 longer than that drawn on Plate III. Though the hinge was not seen, 

 this species seems allied to Limatulina than any other genus of the fam- 

 ily. Confined to the strata above congl. II, chiefly near the very top- 

 of the Waverly as exposed in the county. 



Sirehlopteria media, sp. n. 



(Plate III, Figs. 8-9.) 



(Cf. L. simUls, Walcott.) 



Closely allied to S. simiHs, Walcott, of medium size, rather broad- 

 ly ovate, not oblique, moderately convex near the beaks. 



Left valve most convex, anterior ear broadly rounded, depressed, 

 separated from the body of the body of shell by an abiupt inclination, 

 sinus moderately concave, remainder of the margin a rather regular 

 convex curve ap[)roaching a straight line nenr the point of union with 

 the hinge, which is short, and not forming a well-defined posterior ear; 

 beak acute, somewhat projecting; greatest convexity a short distance 

 from the beak; surface marked by rather distant and coarse, but in- 

 conspicuous radiating striae, or apparently smoodi. The right valves 

 differ little in form, but the byssal sinus is very sharp and deep and 

 the anterior ear is long and rather prominent and separated from the 

 body of the shell by a deep groove. The posterior ear is obsolete. 

 The surface is nearly smooth, except the anterior ear which is very 

 strongly marked by radiating striiP. 



From S. similis this species differs in being relatively broader, es- 

 pecially in the left valves, and lacking the fine striations seen in small 

 specimens of that species. It resembles very closely indeed, C)einpec- 

 tcn foerstii of the coal-measures, but differs from it in the proportions 

 of the ears and does not seem to possess the crenulated hinge. The 

 only other American species with which comparison is necessary is 6". 

 tc7milineatus, from the coal-measures of the West. 



Height of a right valve 16 mm ; greatest length 16.8 mm ; length 

 of anterior ear 7 mm; distance from hinge line produced to anterior 

 angle of shell below byssal sinus 5 mm. Height of a left valve 19 

 mm ; length 19 mm; length of anterior ear 6 mm ; greatest length at 

 about 10 mm. from beak. Numerous closely agreeing specimens from. 



