WHITEAVES. ] DEVONIAN FOSSILS OF MANITOBA, ETC. 297 



strongly inflated in the umbonal region, but obliquely compressed in the 

 antero-ventral : anterior side short, narrow and abruptly rounded or some- 

 what pointed : posterior side broader and much longer than the anterior, 

 its extremity rather narrowly rounded, but rather more broadly curved 

 below than above : cardinal margin nearly straight immediately behind 

 the beaks, thence rising into a short and not very prominent, obtusely 

 angular alation about half way between the beaks and the posterior end 

 (at least, in the largest specimen collected, the original of fig. 10), and 

 ultimately sloping very gradually downward ventral margin gently con- 

 vex posteriorly, but straight anteriorly • umbones rather broad . beaks 

 curved inward and forward, placed near the anterior end. Surface con- 

 centrically sti-iated. Hinge dentition and muscular impression.s unknown. 



Maximum length of the specimen figured, tifty-tive millimetres ; great- 

 est height of the same, thirty-two mm. 



Lake Winnipegosis, on the south-west side, at a small island off Weston 

 Point (five specimens), and on the sovithern shore of Dawson Bay, at the 

 second small point east of the mouth of Bell River (two specimens) ; J. 

 B. Tyrrell, 1889. 



(S.) MODIOMORPHA PARVULA. (N. Sp.) 



Plate 38, tig. 11. 



Shell very small, averaging from a little over half an inch to three- 

 quarters of an inch in length, about one-third longer than high, and high- 

 est at the posterior termination of the cardinal margin. Valves mode- 

 I'ately convex, most prominent and subangular on each of the posterior 

 umbonal slopes, but obliquely compressed on the antero-ventral and post- 

 erodorsal sides of these slopes. In some specimens there is a shallowly 

 concave depression immediately in front of the umbonal slope. Anterior 

 side narrow and very short, forming a .small abruptly rounded lobe below 

 and in front of the beak : posterior side longer and broader than the 

 anterior, its outer margin curved convexly and more or less obliquely 

 downward above, and ultimately forming a somewhat pointed junction 

 with the base below : cardinal margin rather long, straight and ^'ery gently 

 ascending behind the beaks : ventral margin nearly straight, but slightly 

 concave in the centre : beaks minute, depressed, curved inward and for- 

 ward, anterior, very nearly but not quite terminal. 



Surface nearly smooth, marked only with fine concentric stri;e, or mi- 

 nute lines of growth. Anterior muscular impression large, placed close 

 to the anterior margin, and below the beaks. Posterior muscular impres- 

 ,sion, pallial line and hinge dentition unknown. 



Maximum length of the specimen figured, fourteen millimetres ; greatest 

 height of the same, nine mm. 



