OSTRACODA. 637 



Leperditella canalis.] 



Prof. T. Rupert Jones recently described two species from Canada (Contri. Can. 

 Micro-Pal., pt. 3, 1891), that maybe congeneric with these species, viz.: Leperditia 

 ? obscura and Tsochilina lahellosa, the latter appearing to be much like L. tumida. 



Leperditella canalis, n. sp. 



PLATE XLITI, FIGS. 1-3. 



Size.— Length, 1.78 mm.; hight, 1.22 mm.; thickness (L. V.) 0.59 mm. 



Carapace ovate, widest posteriorly, tumid, the point of greatest thickness but 

 little behind and beneath the center; anterior outline semicircular; dorsum straight, 

 not angular in front, and quite obtuse behind, posterior margin somewhat obliquely 

 rounded, scarcely truncated above; near the ventral edge of the left valve a distinct 

 channel or groove, deepest centrally, has suggested the name. Surface smooth. 



This species is closely related to L. tumida Ulrich, occupying a similar geological 

 position in Kentucky and Tennessee, and of which a right valve is figured for com- 

 parison on plate 45, (figs. 13 — 15), The outline in that species however is not so 

 regularly rounded in front, nor so full antero-ventrally, the greatest convexity is 

 more posterior and scarcely so great, and the dorsal angles more distinct. But the 

 feature particularly relied on in distinguishing the two species is the groove along the 

 ventral border of the left valve in L. canalis, the Kentucky form being without this 

 peculiarity. 



Formation and locality.— Lois qx limestone of the Trenton formation, Minneapolis, Minnesota. 



LfiPEEDITELLA PEESIMILIS, H. Sp. 

 PLATE XHI], PIGS.4-6, 



Size. — (E. C.) Length 1.75 mm.; hight 1.23 mm.; thickness 0.8 mm. 



Carapace ovate, moderately convex, with the ends nearly equal; no dorsal angle 

 behind but a well marked one in front; ventral overlap distinct; dorsal edge thick, 

 shoulder like; greatest thickness central; suface smooth. The length varies between 

 1.5 mm. and 2.5 mm. 



At first sight this species looks very much like L. canalis, but carefully compared 

 they prove quite distinct. The outline is somewhat different being less wide (high) 

 posteriorly, the dorsal angles are reversed, and the dorsal edges much thicker, while 

 the thickness of the carapace is less and the ventral groove, which marks the left 

 valve in that species, wanting; Similar diflPerences distinguish it from L. tumida. 

 Aparchites ellipticus holds about the same size and is not very different in outline. 

 Still as its valves do not overlap ventrally and as it has no dorsal angles and really 



