182 | Records of the Indian Museum. LV Gr. Valet. 
which is considered to be identical with Veronicella, Blainville 
(17). Healso described the anatomy of these three species. 
The genus Atopos is mainly defined by the following charac- 
LCES 2 
The body is thickest at the junction of the anterior one- 
third and posterior two-thirds, with a median keel on the 
dorsal surface of the mantle (notum); the transverse section 
of the body forms an isosceles triangle with a short base (formed 
by the foot); the female generative aperture is situated close 
to the anus and the renal and respiratory apertures in the groove 
between the mantle and the sole, a little behind the male gen- 
erative aperture (although a little distant from it); the male 
generative aperture is situated behind the right lower tentacle. 
Simroth also separated a few other species of Vaginula and 
placed them in a new genus which he named Prisma. The genus 
is characterized by the body of the animal being prismatic in 
transverse section. 
Before the publication of Simroth’s paper (12), Heude 
founded another genus Rathouisia for Vaginulus sinensis, the 
name of which he changed to R. leonina. ‘The characters of the 
genus Rathouisia are briefly as follows :— 
The animals are elongated, limaciform ; the mantle is not 
slimy; the upper tentacles are long; the lower tentacles are 
bifid; the posterior end of the foot is pointed, and extends 
beyond the mantle. The male generative aperture is placed 
behind the right lower tentacle. The female generative aperture 
rather approaches the male one, and is placed a little behind it, 
the anus and the excretory and respiratory apertures are placed 
close'to the female generative aperture. 
Later on, Heude united the genera Atopos, Prisma and 
Rathowisia to establish a separate family Rathouistidae, charac- 
terized by a keeled mantle, male and female generative apertures 
distant and the anal and respiratory apertures placed near the 
female opening, in contradistinction to the absence of a keel, 
the position of the female generative aperture on the right in 
the middle of the body and that of the anal and respiratory 
apertures nearly at the posterior end of the body in the family 
of Vaginulidae (7, II). 
In 1900 Babor (2) established a new subgenus Podangia 
for Atopos schildit which differs from other species of Atopos 
in the following characters. The body of the animal is slender 
and high, with a distinct head separate from propodium. The 
foremost part of the notum is bent over the head covering it 
as a hood. The ommatophores (upper tentacles) are short, 
thick and distinctly annulated. Under each ommatophore is 
a crescent-shaped flap of integument produced into a process 
on each side and blended with the lower tentacle and the integu- 
ment on the side of the mouth. Thesurface of the mantle is 
uniformly granulated with scattered tubercles in addition. The 
sole is small, with finely wrinkled border and with numerous 
