242 NEW YORK STATE MUSEUM 
versely heart-shaped in the younger [pl. 33, fig. 3]. The organ was slender 
and relatively long; in the larger specimen it extends, incomplete as it is, 
to the third sternite. The appendage of the second sternite has not been 
observed. | 
Ornamentation. ‘The ornamentation of this species is characterized by 
the small size, but immense number and round circular form of the scales 
and tubercles. The carapace uniformly bears small tubercles, giving it a 
shagreen surface. The coxa, the metastoma and the muscular joints 
of the walking and swimming legs have somewhat larger scales most of which 
have the form of slightly tilted disks with the anterior segment cut away 
or submerged in the periderm, the posterior portion being raised. The 
tergite of a mature individual bears rather widely scattered, larger semi- 
circular to low triangular scales which terminate rather abruptly 
or become fewer and smaller over the posterior doublures but con- 
tinue on their overlapped anterior parts. On the sternites the scales 
are arranged in distinct bands, the anterior halves of the plates being 
covered with such a densely crowded mass of small semicircular scars 
that the naked eye fails to discern them. These increase in size to 
the middle of the sternite where they form a zone of larger semi- 
circular to crescentic scars which are less densely arranged and become 
farther separated posteriorly until they almost entirely disappear above 
the doublure. Between these larger scales numerous small ones, often 
of microscopic size, are interspersed. The opercular plates differed from 
the other sternites in being almost entirely covered with the larger scales 
which are much more densely arranged than on the following plates, but 
are also lacking along the posterior border. The pentagonal and sagittate 
basal portions of the female genital appendage are ornamented like the 
opercular plate. | 
The postabdomen, as a whole, bears scales of the size and distribution 
of those on the tergites. They lengthen, however, posteriorly, approx- 
imately in proportion to the remarkable lengthening of these postabdominal 
segments until on the last segment they have becoine acutely pointed. 
