WHITEAVES.J DEVONIAN FOSSILS OF MANITOBA, ETC. 301 



NucuLA LiRATA, Coiirad. 



Xueula /iraia, Conrad. 1842. Journ. Ac. Nat. ,Sc. Phil., vol. VII, p. 250, pi. xv, 

 fig- 7. 

 " Hall. 1870. Prelim. Not. Lamellibr. Shells, 2, p. 3. 



1883. Pal. St. N. York, vol. V, pt. 1, Plates and Explana- 

 tions, pi. xlv, figs. 17-27. 



1885. Pal. St. N.York, vol. V, pt. 1, Lamellibr., 2, p. 316, pi. 

 xlv, figs. 5, 11, 15, 17-22, 24, 25, and pi. xciii. 



North side of Manitoba Island, Lake Manitoba, J. B. Tyrrell and J. 

 F. Whiteaves, 1888 : two or three badly preserved single valves. 



(S-) NucuLA ? Manitobensis. (N. gp.) 



Plate 41, fig. 1. 



Shell rather small, ovately trapezoidal, about one-third longer than high 

 and very inequilateral. Valves gibbous, tumid in the umbonal region 

 and above, but obliquely compressed and somewhat depressed in the centre 

 below : anterior side (assuming it to be a Mucula)* much longer than the 

 posterior, its outer margin obliquely subtruncate above and forming an 

 obtusely pointed junction with the base below : posterior side extremely 

 short, its margin concave immediately under the overhanging beaks and 

 narrowly rounded below ; cardinal margin gently convex, curving rather 

 rapidly downward posteriorly : ventral margin nearly straight for the 

 greater part of its length, but curving upward abruptly at both ends : 

 umbones broad, depressed, anterior, terminal : beaks curved inward, for- 

 ward and a little downward. 



Surface apparently almost smooth and marked only with faint concen- 

 tric strife of growth. Hinge dentition and muscular impressions un- 

 known. 



Length of the largest specimen collected, nine millimetres ; greatest 

 height of the same, six mm. and a half. 



Dawson Bay, Lake Winnipegosis, on a small island north of Whiteaves 

 Point, and on its south-western shore, at an exposure about two miles 

 west of Salt Point, J. B. Tyrrell, 1889 : a single right valve from each of 

 these localities. 



As the characters of the interior of the valves of this species are entirely 

 ■unknown, it is quite uncertain to what genus it should be referred. It 

 is here provisionally regarded as a ICucula on account of its general resem- 

 blance, in external form, to some varieties of the JV. varicosa of Hall, as 

 figured on Plates xlvi and xciii, of vol. V, Pt. 1, (Lamellibr., 2) of the 



* Dr. S. P. Woodward (Manual of the MoUusca., p. 269) says that in Nucula the 

 umbones are "turned to the short, posterior side." 



