29 



five and six. The last two whorls of this specimen are sepai-atod by a 

 space equal to more than double the diameter of the thickest unex- 

 panded part of the cast of the tube of which the body- whorl is com- 

 posed. In another specimen, the original of figure 8a. on plate 4, in 

 which four of the earliest whorls are J)reserved, the diameter of the 

 cast is five millimetres at the largest and a little more than one milli- 

 metre at the smallest end, and the volutions are separated by spaces 

 somewhat wider than the maximum diameter of the cast of the tube. 

 It would appear, therefore, that the entii e number of volutions is about 

 seven or eight, and that the later whorls arc rather more widely 

 separated proportionately than the earlier ones. 



Although it has been thought best to give a provisional name to the 

 specimens above described, as a matter of convenience, it is not at all 

 unlikely that they may prove to be monstrosities or abnormally 

 developed individuals of some regularly formed species of MurcMsonia, 

 to which they may bear the same morphological relationship as the 

 well-known but exceedingly rare scalariform varieties of the living 

 Selix aspersa of Muller, figured by Moquin Tandon and Chenu, do to 

 the ordinary form of that species. Of all the species of MurcMsonia 

 from the Guelph formation known to the writer, these singularly con- 

 structed shells seem to come nearest to M. macrospira, partly in the 

 number and contour of their volutions, but more especially in the 

 breadth and slight elevation of their rounded spiral band or carina. 

 The fragment represented by figure 9 on plate 4 is a portion of a cast of 

 a shell from Durham, which appears to be intermediate in its cha- 

 ractei-s between M. soluta and some normally developed species of 

 Murchisonia, perhaps M. macrospira. The whorls of this fragment 

 although free and disconnected, ai'e still somewhat approximated, and 

 its spiral keel is precisely like that of M. soluta. 



The JEnomphalus circinalis of Goldfuss is a good example of an almost 

 completely uncoiled species of that genus, but its apical whorl is repre- 

 sented as being regularly spiral. 



Murchisonia tropidophora. (N. Sp.) 

 Plate 7, figs. 5 and 5a. 



The above name is proposed for a remarkable shell, of which only 

 one imperfect specimen is known to the writer, and for which a new 

 genus may have to be constituted. This specimen has about one-third 

 of the apical or posterior end broken off, and the remaining portion 

 consists of a shelly tube which increases rapidly in diameter, especially 

 near and at the aperture, and which is obliquely, spirally and tightly 



