RATTULIDA. 67 
The hinder body is ventricose, greatly overhanging the foot. There is a great aggregation 
of minute air-(or oil-)globules in the dorsal cavity. The trophi I supply conjecturally. 
Dr. Collins has added to his figures the following note: ‘‘ Head very large ; rotatory 
organ compound ; a large eye ; peculiar ganglionic mass or brain lying on dorsal surface. 
Two toes, which it sometimes crosses ; peculiar from being very wide apart, and de- 
curved, as the toe of Rattwluws lunaris. Found in a pool near Wellington Military 
College, Berks.” —P.H.G.] 
Length. Unrecorded. Habitat. As above. 
Genus C@LOPUS, Gosse. 
[GEN. CH. Body cylindrical, curved ; foot bulbous, inclosed ; toes, one broad plate 
with another laid upon it, in a different plane. 
A very remarkable deviation from normal structure is found in the species thus asso- 
ciated. Instead of two toes, consimilar and coequal, placed side by side right and left, 
like the legs of a man; here are two toes very unequal, hollow triangular plates of like 
shape, but of diverse dimensions, the smaller lying within the hollow of the larger. 
¥o use a homely comparison, let us suppose the bowl of a tablespoon, broadly truncate 
at the top and drawn out to a long point; then the bowl of a teaspoon of exactly the 
same shape, laid smoothly in its hollow; the two separately articulated to the foot-bulb, 
so as to be capable of independent motion to a slight extent. 
These organs are so anomalous that it is hard to deseribe them as “‘ toes.”” If it could 
be proved that the cloaca opens between them, we might say without hesitation that the 
larger and upper represents a true tail, the smaller and lower a stylate toe. But I have 
no knowledge on this point ; which could be settled only by a rare accident,—the obsery- 
ing of the act of evacuation at the moment when the animal was viewed laterally. 
In general figure and organization, there is so close an agreement with the former 
two genera, that the family affinity is indubitable. Several species I am able to asso- 
ciate as manifesting this structure: and, what is very curious, I have found it exhibited 
by a member of a remote genus,—one of the Coluri (q. v. infra). 
It is possible that Ehrenberg's Rattulus lwnaris may represent my C. porcellus. 
But the absence of any detailed diagnosis, in his text, leaves it doubtful; while his 
assigning of two eyes to his species is against the identification. The Diwrella rattulus, 
Hyf., described and figured by Herr Eckstein, may possibly be the same thing. The delicate 
lines that are drawn through the middle of the toe, in his engraving, may be either the 
inner edges of two normal toes, or the outer edges of a single superposed toe ; and the 
closest examination does not determine this. If the former, it is a species of my genus 
fiattulus; if the latter, a Calopus. His text also is ambiguous. ‘‘ Two toes, long, 
much bent bellyward, and slender,” seem to point to Rattulus ; while “‘ at their base they 
do not stand close side by side, but lie with their points one on the other,” appear to 
indicate the peculiarity of Celopus, ill-understood.—P.H.G.] 
C. PoRCELLUS, Gosse. 
(Pl. XX. fig. 18.) 
Monocerca porcellus 5 ¢ é : Gosse, Ann. and Mag. Nat. Hist. Sept. 1851. 
[SP. CH. Body cylindric, short and plump ; lorica ridged ; head with two pro- 
jecting spines ; the longer toe equal in length to the depth of the body. 
This neat, plump little creature always reminds me of a fat young pig. The general 
form may be compared to that of a well-filled sausage, a little bent, as sausages often 
are, and the varying shades of brown colonr produced by the distended stomach and 
FE 2 
