[MATTHEW] STUDIES ON CAMBRIAN FAUNAS lOl 



" [>S'i>e.]— Length of aperture about 1 to 1| lines [3^ mm.] ; width 

 about one line [2 mm.] ; height of the shell about 1 line. 



" [Localitij and Horizon].— Occnrs in the red limestone at Brigus, 

 Conception Bay." 



I find a few specimens answering to this description ; the ridges are 

 somewhat irregular, and there are concentric striœ of growth. These 

 shells are all compressed laterally, indicating that they had a narrow oval 

 aperture. 



Mr. Walcott reduces this species to a variety of Stenotheca rugosa, 

 Hall. On comparison with examples from Troy, I do not find that the 

 shells from Smith Sound are conspecific. Those from Troy are finely 

 granulated and have about nine ridges of growth ; those of Smith Sound 

 are concentrically striated and have only four or five ridges. The Troy 

 specimens stand ei-ect on their apertural base, these are found lying on 

 their side in the limestone bed. 



The generic name Stenotheca has been applied to shells of this form 

 by various authors ; it is not used here for reasons given in Trans. Roy. 

 Soc. Can., vol. viii., sec. iv., p. 132. 



PLATYCBRAS, Conrad. 



Platyceras transversum (PI. v., figs. 4a and b). 



Platycevas transversum, n. sp., Nat. Hist. Soc. N.B., Bull, xviii., p. 190, pi. i., figs. 

 4a and b. 



A small species of one whorl, with the spire scarcely at all elevated. 

 Aperture campanulate in front, slightly contracted behind. A low carina 

 with a shallow groove on each side extends along the centre of the dor- 

 sum to the aperture. 



Sculpture. — The surface is granulated and marked also by very fine, 

 closely set lines of growth, which are not distinct on the dorsum. The 

 sculpture on this shell resembles that on the ventral surface of a Hyolithes 

 or Orthotheca. 



Size — Length along the whorl to the mouth 6 mm. ; height, 3^ mm. ; 

 length of aperture, 4 J mm. ; width nearly 4J mm. Infrequent. 



The figures given by Mr. Walcott as those of the young of Stenotheca 

 rugosa agree with this species in size and form.^ 



Under Stenotheca rugosa Mr. Walcott figures a shell from Troy, N.Y., 

 which resembles this species." 



1 U.S. Geol. Surv. Bull. 30, pi. xli., figs. Id and e. 



- U.S. Geol. Surv. "Olenellus Zone," pi. ixxiv., figs, l/i and li. 



