73 



Irvine rocks, Elora, J. Townsend, 1885 : one specimen with the test 

 preserved. Ti'he apex is imperfect, but the three latest Tolutions of the 

 spire, and most or the outer volution, with the characteristic alation of 

 each, are well preserved. 



The shell for which the foregoing name is suggested, may prove to be a 

 variety of P. Valeria or of F. alata, but the surface markings of its apical 

 side seem to be very different to the corresponding markings of either of 

 those species. 



Pleurotomaeia Halei, Hall. Var. 



Plate 10, figs. 2 and 2 a. 



Pleurotomaria Halei, Hall. . .1861. Rep. Sup. Geol. Surv. Wiscons., p. 34. 



" . . .1865. Extr. in adv. of Eighteenth B,ep. on the N". Y. 



St. Cab. Nat. Hist., p. 34*. 

 .,.1867. TwentiethRep. Reg. N. Y. St..Cab. Nat. Hist., 

 pi. 15, figs. 13 & 14. 

 Cfr. Pleurotomaria limata, Lindstrom. 1884. Silur. Gastr. and Pterop. Gotland, 

 p. 114, pi. 10, figs. 2-17'. 



Shell conical or turbinate conical, much broader than high, and deeply 

 though not very widely umbilioated. Volutions probably four or five 

 when perfect, though only the three later ones are preserved in the speci- 

 mens collected, those of the spire ventricose or expanded, the penultimate 

 volution distinctly angulated anteriorly, in some specimens, such as the 

 one figured, a little below the middle, and in others at or near the base 

 and next to the suture below. Outer volution widely expanded, a little 

 higher than the spire, obliquely convex near the suture and faintly con- 

 cave next to the alate periphery above ; encircled about the midheight 

 with a prominent, but apparently non-spinose, alate keel four millimetres 

 and a half in altitude, which incloses the slit band ; rather strongly con- 

 vex beneath, but depressed and deeply umbilicated in the centre, the 

 umbilicus occupying about one-third of the diameter of the base, though 

 its margin is rounded and indefinite. 



The surface markings of the umbilical side are well preserved in most 

 of the specimens collected, and consist of crowded, flexuous, striae of growth, 

 which curve obliquely and concavely backward from the peripheral alation 

 to the umbilicus, and are crossed by spiral incised lines. The crescents 

 of the slit band are crowded, but they are not sufficiently well preserved 

 to show the details of the irstructure. The surface ornamentation of the 

 apical side is not nearly so well exhibited, but it appears to consist of 

 numerous and closely disposed lines of growth, which are crossed by one or 

 more spiral ridges. 



Durham, J. Townsend, 1882-89 : nine specimens. As seen from above, 

 these specimens bear a certain general resemblance to P. Elora, Billings, 



