CAMBEO-SILUEIAN OF MANITOBA. 81 



Siphuucle exogastric, and placed very near to the dorsum, but not quite marginal. In the 

 original of fig. 4 on Plate XV, which is an artificial and longitudinal section through 

 the centre of a specimen from Bull's Head, the siphuncle is nearly cylindrical, but very 

 slightly expanded between the septa and as slightly contracted where it intersects them. 



Dimensions of the most perfect specimen collected :— actual length along the median 

 line of one of the sides, 129 mm. ; estimated total length of the same, when perfect, 

 133.5 mm. ; maximum dorso-veutral diameter of the same, 34.5 mm. ; greatest lateral 

 diameter, 31.5. 



Big Island, Doer Island, Punk Island, Big Grindstone Point, Bull's Head, Dog's 

 Head, and Pike Head or Jackfish Bay, Lake Winnipeg, T. C. Weston, 1884. One nearly 

 perfect specimen is from Big Island (Plate XIII, fig. 3) and another from Bull's Head 

 (Plate XV, fig. 4) the rest being for the most part only pieces of the posterior and septate 

 portion of the shell. 



Deer Island, Lake Winnipeg, J. B. Tyrrell, 1889 : the most perfect specimen known 

 to the present writer, the original of fig. 4 on Plate XIII. 



Trochoceras McCharlesi. (N. Sp.) 

 (Plate XVI.) 



Shell very large (the only specimen known to the writer, which is septate through- 

 out, having a maximum diameter often inches and a half) and composed of about three 

 apparently separate but closely contiguous volutions, which are circular in transverse 

 section and which increase rather slowly in size : they are also slightly asymmetrical 

 and enrolled on very nearly but not quite the same plane, the spire being sunk a little 

 below the highest level of the outer whorl. 



Surface of the outer A^olutiou marked by very numerous, close-set, rounded and 

 llexuous ribs, which are rather narrow but unequal in size, with an average breadth of 

 about three millimetres. Across the sides the ribs curve obliquely and more or less 

 convexly backward, and on the periphery they form a series of broad, shallowly concave 

 and backwardly directed sinuses. 



The suturai lines run parallel with the ribs on the test, but are placed much further 

 apart, the average distance between the septa being about nineteen millimetres. Position 

 of the siphuncle unknown. 



The writer has much pleasure in associating with this fine species the name of its 

 discover, Mr. A. McCharles, formerly of Winnipeg, to whom the Survey is indebted for 

 many choice and some apparently unir[ue specimens of fossils from that part of the Red 

 River valley which runs through Manitoba. The specimen figured, which is represented 

 as slightly smaller than the natural size, and which is now in the Museum of the Survey, 

 was collected by Mr. McCharles in 1884 at East Selkirk. About one third of this speci- 

 men has been broken off, but the part remaining presents a very instructive transverse 

 section of the shell at a right angle to the direction of the volutions. A considerable 

 portion of the test is well preserved on the outer volution, and in those places where the 

 test has been accidentally removed, the characters of the septa are well shown. The two 



Sec. IV, 1889. 11. 



