302 



Museum of the Survey, the largest of which is fully four inches in its 

 greatest diameter. One of these specimens still bears the original written 

 label ; " Mingan. Clear Water Point. L. 1859 ; " the L. of course meaning 

 Logan. This is the locality referred to on page 134 of the " Geology of 

 Canada" (1863) as the bay "above Clear Water Point," where the lowest 

 part of the Chazy formation is said to be visible. A section of the rocks 

 exposed at this locality is given, part of which id said to consist of twenty 

 feet of " grey nodular limestone with Columnaria parva, Stenopora ad- 

 hcerens, Fenestella inaepta, Opthis piger, Strophomena inorassata, Gteno- 

 donta nasuta. Nautilus Jason, Amphion Canadensis, Harpes antiquatus, 

 and Illcenus globosus.'' Clear Watei' Point is on the north shore of the 

 Gulf of St. Lawrence, opposite to the Mingan Islands. 



In the same Museum there are two other specimens of Plectoceras Jason. 

 One of these is a large and imperfect but characteristic specimen, labelled 

 as having been collected at St. Charles Island by J. Richardson in 1860; 

 and the other, labelled only " Mingan." 



(2.) Plectoceras Halli, Foord. (Sp.) 



Plate 35, figs. 3, 4, and 4 a. 



. iTMchus undatus (para) Conrad 1.812. In Emmons' Geol. New York, pt. II, 



Surv. Second Geol. Distr., p. 394, no. 104, 

 " fig. 2, edge view ;" probably, though the 

 figure is diagrammatical and apparently 

 inaccurate. 



iiiuiies «n<fot«s, (pars) Hall 1847. Pal. N. York, vol. I, p. 52, pi. 13, 



figs. 1 a aud 1 b. 



II II (pars) Emmons 1855. Amer. Geology, pt. II, p. 146, pi. 5, 



fig. 14 a ; probably. 



Cryptoceras undatum, Chapman 1857. Canad. Journal, N.S., vol. II, No. X, 



p. 267 ; and Annals and Mag. Nat. Hist. , 

 Second Series, vol. 20, p. 107. 



Lituites undatus, Billings 1863. Geol. Canad., pp. 156 and 951. 



Trocholites undatus, ipaxs) Hysttt 1883. Proo. Boston Soo. Nat. Hist., vol. 



XXII, p. 267. 



Trochoceras Halli, Foord 1891. Cat. Fossil Oephalop. Brit. Mus., pt. 



II, p. 42, figs. 4 a, and 4 6. 



Plectoceras obscurwm, Hyatt 1894. Proc. Amer. Philos. Soc, vol. XXXII, 



p. 445. 



Plectoceras Halli, Whiteaves 1903. Ottawa Naturalist, vol. XVII, p. 120. 



This is the shell that Dr. Foord separated from the Lituites undatus of 

 Hall in 1891, and described and figured under the name Trochoceras 

 Halli. The specific characters of T. Halli are said to be as follows : 

 "The shell, which is not complete, consists of two volutions; the 

 asymmetry is slight, but quite discernible. The shell increases its dia- 

 meter about three times in the last volution. The section is distinctly 



