42 



This species occurs at South Point, S. W. Point and the Jumpers ; Div. 

 3, 4, A. G. 



It is probably only a variety of 0. elegantula. 



0. UBERis, B.= (9 cequivalva, Shaler, op. cit., p. 56. — I propose to 

 change the name given by Mr. Shaler to this species as it is equivalent to 

 cequivalvis, already applied by both Davidson and Hall to other forms of 

 the genus. The following is the description in the work cited. 



" Shell somewhat lenticular ; one fifth wider than from beak to border ; 

 valves nearly equal in convexity ; toothed valve a little the most prominent ; 

 hinse-line rather more than half the width of the shell. Toothed valve 

 strongly evenly convex, a little depressed opposite the umbo ; umbo rising 

 above the hinge-line about one sixth the distance from beak to border, a 

 little laterally compressed ; beak minute, scarcely projecting beyond the 

 hinge-line, a little recurved ; area about twice as wide as that of socket 

 valve ; width one-sixth of length ; steeply sloping ; most convex point of " 

 valve a little nearer the beak than border. Socket-valve nearly evenly 

 convex ; very slight mesial depression, extending from the umbo to the 

 centre of valve, where it fades out, and in succeeded by a slight ridge, 

 which extends to the border, beak distinct ; not rising as far above the 

 hinge-linge as that of opposite valve by the width of socket-valve area. 

 Surface with fine dichotomous striae with interspaces as wide as the 

 ridges." 



Mr. Shaler, at the commencement of his description, says " QS^n. Orthis 

 hyhrida, Billings.) " I cannot, however, discover in what publication I 

 have designated this fossil by that name. It is most abundant at Junction 

 Cliff but it occurs throughout Divs. 1, 2, 3, 4, A. G. 



0. RHYNCHONELLIFORMIS, Shaler, op. cit., p. QQ. — This is a variety of 

 0. uberis with a short hinge-line and with a mesial sinus in the ventral 

 talve of some of the individuals. It occurs most abundant at Gull Cape ; 

 Div. 2 : more rarely 1 mile east of Jupiter River, Div. 3 ; The Jumpers, 

 Div. 4, A. G. 



0. RUIDA, n. sp. — Shell sub-lenticular, both valves moderately and 

 nearly equally convex : hinge-line a little less than the whole width ; sides 

 and anterior angles irregularly rounded ; front with a portion in the mid- 

 dle somewhat straight. Ventral valve with a strong broadly convex fold 

 along the middle dying out on the umbo ; on each side of the fold nearly 

 flat ; umbo small ; area moderate, forming an obtuse angle with the plane 

 of the lateral margin. Dorsal valve with a deep sub-angular sinus which 

 tapers to a pomt at the beak ; on each side of the sinus moderately con- 

 vex ; cardinal angles compressed ; area small. Surface with small, rough, 

 sub-angular ribs, several times divided before reaching the front ; four or 



