318 COXTRIBUTIONS TO CANADIAN PAL^iEONTOLOCiy. 



l)aiid, which is neither groo-\-ed in the middle nor margined on Ijoth sides 

 \>j an impressed Hne or minute keel. 



Surface marked with flexuous raised lines which curve gently and 

 con\exly forward on each side of the slit band, and backward to the 

 closed umbilicus. 



^^'estern shore i.)f Dawson Bay, Lake AN'innipegosis, " fi'om slabs 

 apparently derived from the neighbouring cliiis," J. W. Spencei-, 1H74 : 

 one cast of the interior of the shell. Lake Manitoba, at Monrfie and 

 Onion Points, and at an exposure a little to the north of Steep Rock 

 Point, J. B. Tyri-ell and J. F. Whiteaves, IHSS. Lake Winnipegosis, — at 

 Snake Island, at an island off Weston Point, at South Manitou Island, 

 at Point Brabrant, and at four different exposures in or around 

 Dawson Bay ; also on the Red Deer River, a mile and a half above the 

 Lower Salt Spring : J. B. Tyrrell and D. IS. Dowling, 1889. One or at 

 the most two specimens weie obtained at each of these localities. 



Altogether, nineteen specimens were collected, and, of these, thirteen 

 ai'e mere casts of the intei'ior of immatui'e shells, five are either very small 

 or not fully grown specimens with most of the test preserved, and one, 

 as previously stated, is an imperfect cast of the interior of an adult shell. 

 Not a vestige of the columellai- callosity of the inner .side of the aperture 

 is preserved in any of them. 



The whole of the specimens are so imperfectly pi'eserved that it is 

 doubtful whether they should be regarded as specifically identical with 

 J>. Peliij>x or not. The only points in which they seem to differ from that 

 spjeoies, as described and figured by Pi-ofessoi- Hall, are that they seem to 

 attain to a nmcli laiger size when adult, and that the closing of the 

 umbilical cavity on both sides of immature individuals is not caused by 

 a spreading over it of the columellai- callus. Small specimens of the 

 species now under consideration are very similar, in shape and sculpture, 

 to the B. ]>ro})i-)i,qims of Meek*, from the Corniferous limestone of Ohio, 

 but that species is narrowly umbilicated and its slit band is said to be 

 "furrowed along the middle, so as to pre.sent a biangular appearance." 



(S.) PoRCELLiA Manitobensi.s. (Nom. Prov.) 



Plate 42, figs. 4 and 4a. 

 Perhaps ;i var. of Poraillia, nt/ri(t,ta, Goldfuss. (Sp.) 

 I.'fr. PJiiomj'ilia/nK s/ria/iin, (iofdfiiss. 1S41-44. Petref. Oenuaii., vol. 1)1, p. S4, 

 pi. cl.vxxix, figa. 15, a, b, c. 

 P/i'AirotoinarialjiJi<la,(J,. and F. Sandberger. IS-JO-fiK. Die Veistein, des Rheiniscli. 

 Scliicliteusyst. in Nassau, p. IS."), pi. x.-;ii, fig.s. 10, 10a, b. 

 PorccJIid nIriuAa., KoUcn. IHH!). Uuber die Eiitwiokel. der (Jastrop. voin 

 (Jambr. bis zur Trias : ,Sep.-Abdr. ans duni Neuen Jahrbuch 

 fur Mineralog. , cite., Keilageband ^'T. , p. 401. 



*Kep. Geol. Soc. Ohio, vol. I, pt. 2 (1873) p. 22(), pi. xx, tigs. 4a, b. 



