CAMBRO-SILURIAN MICRO-PALiEONTOLOGY. 51 



PRIMITfA ? (? BeYRICHIA) PARALLELA. (N. sp.) 

 PI. IX., figs. 7-7a.''- 



Valves oblong subquadrate, about twice as long as high, and modej. 

 ately convex. Ends subequal, sometimes slightly truncate, the pos- 

 terior one more blunt than the anterior. Dorsal and ventral margins 

 nearly pai-allel. Anterior margin with a thick and strongly elevated 

 border, extending slightly beyond the contact margin. Posterior mar- 

 gin also with a border, which is not nearly so much elevated there as at 

 the anterior end, being in many cases almost flat. Along the ventral 

 margin the border is obsolete. A well-marked sulcus extends from 

 about the middle of the dorsal line to near the centre of the valve. At 

 the posterior side of the sulcus a rounded node is more or less complete- 

 ly separated from the posterior lobe by a branch of the main sulcus. 

 In a dorsal view the anterior lobe is very slightly more convex than 

 the posterior, while the anterior border is quite as prominent. In an 

 end view the point of greatest convexity is a little above the middle. 



An average specimen gave the following measurements : greatest 

 length, 0.8 mm.; greatest height, 0.4 mm. ; greatest convexity of one 

 valve, 0.13. 



This species is represented in the Manitoba material before me by 

 two imperfect valves. Fig. *7 (pi. IX), was intended to represent one 

 of these, but it is now known that the illustration is faulty in failing 

 to show an important feature, which, when added, gives it quite a 

 different appearance. 



Several years ago I washed a considerable quantity of shale from the 

 upper beds of the Hudson Kiver or Cincinnati group at Oxford, Ohio. 

 The residue of these washings has as yet not been picked over, but a 

 short time ago I spent an hour in looking over a small lot of the 

 material, and found that it contained Ostracoda, among them the 

 species under consideration. The specimens are a little smaller than 

 the Manitoba ones, but their specific identity is scarcely to be ques- 

 tioned. The last fact, however, was not recognized by me till I began 

 my final examination of the Manitoba specimens, preparatory to draw- 

 ing up the descriptions. It was then noticed that a thick border, now 

 crushed and partly worn away, actually existed at the anterior end of 

 the valve from which fig. 7 was drawn. The posterior border is very 

 fiiint in this specimen, having evidently also suffered through attrition. 



The distinctive features of the species are (1) the absence of a bor- 

 der along the ventral margin and its development at the two ends, (2) 

 the excessive development and prominence of the anterior border, and 

 (3) the oblong shape and nearly parallel dorsal and ventral margins. 



*Fig. 7 is very faulty, having been drawn and lithographed from a crushed and macerated 

 specimen before the much better examples from Ohio were seen. 



