158 CRETACEOUS GASTROPODA 
classed by Adams (Gen. I, p. 136) in the sub-family Rapayiva, ought to forma 
genus in the T'ricuorroprp#, although Gray (Guide, 1857, p. 77) appears to unite 
it again with Trichotropis. : 
There are only very few fossil forms known which belong to this family. 
Gabb. (Pal. Calif. I, 1864, p. 188, Pl. XXT, Fig. 98) described lately a remarkable 
shell from the cretaceous rocks of California as Lysis duplicosta (n. gen. et sp.), 
which has the general form of Fossar, and partly that of Narica and Stomatia. 
Should it not belong to the Narrerzp# or the Veturinrp#, which is, more likely, its 
only place would be in this family next to Separatista, Gray, although it is, properly 
speaking, very much allied to N. carinata, Sow., sp. (Trans. Geol. Soc. Lond., IV, 
Pl. XVIII, Fig. 8), which is very probably a Possar. 
The jurassic genus Purpurina, D’Orb., includes shells of the Cancellaria-or 
Trichotropis-form, anteriorly with a slightly produced aperture and an obsolete 
notch occasionally. The genus is generally classed with the Bucezwrpz; but if we 
take the total form of the shell and that of the aperture into consideration, there 
is certainly no other family, the species of which possess quite similar characters, 
excepting that of the Trrcuorropmsz. Besides this relation Purpurina offers none 
to any other family excepting the Lirrormipz. 
There are about 14 living species of Trichotropis, a few tertiary, and only one 
doubtful cretaceous species described under this genus by Conrad, 7. cancellaria, 
(Journ. Acad. Nat. Se. Phil. ITT, pp. 333 and 336, Pl. XX XV, Fig. 8) from Missisippi. 
XL, TRICHOTROPIS, Sowerby et Broderip, 1826. 
1. Tricnotroris Konrincxi, Willer, sp. Pl. XIII, Figs. 7—9. 
1851. Trochus Konincki, Miller, Petr. Aachner Kreide, I, p. 44, Pl. V, Fig. 11. 
1864. idem. Pictet, Pal. suisse, 3me. Ser. II, pt. p. 533. 
Trich. testa ovato-turbinata, columella excavata; anfractibus quinis, primis levi- 
gatis, ceteris spiraliter dense striatis, infra mediwm acute carinatis, supra atque infra 
carinam plus minusve excavatis, transversim lamellose costulatis ; costulis ad carinam 
plus minusve acute-elevatis sew coronatis; ultimo anfractu inflato, spira altiore, ad 
medium bicarinato, carina infera tenuiore ; umbilici margine crasse carinato; aper- 
tura ovali, antice subemarginata, marginibus levibus, dilatatis, postice continuis. 
Spiral angle about 70°; sutural angle 12°. 
Height of last whorl : total of shell (considered as 1:00) ... 0'54—0°65. 
The height of the spire is somewhat variable in this species, although the 
number of whorls is usually only five. The last whorl, being, however, more or less 
inflated, covers a greater or smaller portion of the preceding whorls (each respect- 
ively), and the consequence is, that not only the spire becomes shorter, but that 
the carina of each whorl is in the first case nearer to the middle (see Fig. 7), in the 
other nearer to the lower suture (Fig. 8). On the last whorl there is always a second 
