1903] Canadian Specimens of Lituites Undatus. 



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monly mistaken for the young- o{ Eurystomites undatus; but it has an 

 open gyroceran spiral, the siphuncle is nearer the venter, and the 

 costK are more highly developed and more prominent, and have a 

 distinct character from those of that species." 



In 1878, Mr. T. C. Weston visited Lorette, on behalf of the 

 Geological Survey, and succeeded in obtaining- for its Museum n 

 fine series of large and unusually well preserved specimens, that 

 agree very well with Foord's description and figures of r^'OcAcc<?ra.y 

 Halli, but that give some additional information in regard to that 

 species. Some of these specimens, which measure a little more 

 than three inches in their maximum diameter, are apparently adult 

 shells, with the apertural margin well preserved. Their coiling 

 shows only a slight and scarcely trochoceran inflection, and is 

 almost if not quite gyroceraconic The lip of each of the presu- 

 mably full grown specimens is thin, simple, and parallel to the 

 obliquely flexuous ribs, or narrow rib-like plications, and minute 

 ridges, that cross the outer whorl obliquely, and is consequently 

 curved convexly forward orl each side, and both deeply and con- 

 cavely backward on the venter, which is broader than the dorsum. 

 The sutural lines are nearly straight, and the siphuncle is cylindri- 

 cal, ventral and marginal. 



The resemblance between these specimens from Lorette and 

 the Naulilus Jason of Billings, the type ot Hyatt's genus Plectoceras, 

 is very striking, and the close resemblance of similar speci- 

 mens from Lorette, etc., to N. Jason, had not escaped Mr. Billings' 

 notice. Indeed the only practical difference between these species 

 would seem to be that the volutions of N. Jason are a little more 

 losely coiled than those of Trochoceras Halli, and that the siphuncle 

 of the former is placed at a short distance from the periphery or 

 venter. In the present state of our knowledge of this question, 

 the writer is inclined to think (i)that no specimens that exactly 

 correspond with the Inachus undatus of Emmons have yet been 

 found in the Province of Quebec ; (2) that all the specimens from 

 the Black River limestone of that province that have been referred 

 to Lituites undatus are Trochoceras Haiti ; and (3) that the last 

 named species is a Plectoceras and should therefore be call:-d 

 Plectoceras Haiti. 



It may, however, be stated that, in a letter dated August 4th, 



