1864. ] MR, 0. SEMPER ON NEW MOLLUSKS. 251 
exhibiting part of the shell. The figure given by D’Orbigny, in Fé- 
russac’s ‘ Mollusca,’ 76, t. 2. f. 8, exhibits the body contracted, and 
the hinder part produced into a marginal disk, which is said to be lucid 
green and phosphorescent in the dark. The tail is described as 
rounded, and no mention is made of any subcaudal gland of any kind ; 
so that it can scarcely be the genus here described; for the large, 
deep subcaudal circular pit, with its large, thick, prominent rim, 
could not have been overlooked on the most casual examination. 
I have not considered it right to cut into the single specimen 
which we possess of this interesting genus, either to examine the 
existence or form of the shell, or to describe the form, structure, and 
disposition of the teeth—all most important particulars, which I hope 
the receipt of other specimens will enable me before long to supply. 
The pore near the hinder margin of the shield is deep and lined 
with membrane, which is swollen up and bladder-like at the base in 
the specimen in spirits, not showing any indication of a shell; and 
therefore it cannot be (as has been suggested by one zoologist, to 
whom I had showed the specimen) compared to the open space which 
is left on the upper surface of the shell by the edge of the mantle 
being only partially reflected over its outer surface as in the genera 
Drusia, Girasia, Merialla, and Parmacellus in the Arionide, and 
Peitella in the Limacidz. It is probably more properly to be com- 
pared with the luminous gland which is said to be found, but so 
imperfectly and differently described as existing in the genus Pho- 
sphoraxz. 
The mantle is rather produced and free in front and on the front 
part of the sides, but does not appear to be so free as in the Eu- 
ropean species of the genus Limaz. 
URocyYcLuvs KIRKII. 
Pale brown, with minute square black spots on the sides, with a 
black streak on each side of the back; middle of the back with two 
darker brown streaks. The sides of the body with diverging sunken 
lines. The margin of the foot with a series of small black specks. 
Hab. Central Africa. 
5. Descriprions or New Species or Mouuusks, oF THE 
Genera Recistoma AND Puprna. By Orro Semper. 
ReEGIsTOMA AMBIGUUM, O, Semper. 
T. imperforata, ovato-elongata, glabra, nitida, subpellucida, fla- 
vido-grisea, aperturam versus aurantiaca ; spira subacuminata, 
mamillata; anfract. 53, convexiusculi, superiores regulariter 
crescentes, mediani inflatult, ultimus spira breviore, descendens ; 
sutura impressa, filomarginata, callosa; columella parva, in 
adultis angulum obtusum cum peristomate formans, in ado- 
