396 Mr. H. W. Bates on the Longicorn Coleoptera 
Thalassine. I have not yet examined the Paguride in this 
direction. Nowhere else am I acquainted with a similar struc- 
ture of the sternum, except in a Peneus from Manilla, the female 
of which presents a peculiar soft structure on the fifth segment 
of the thorax. This is a round, chitinous, but uncalcified disk, 
which bears an elevated ridge in the middle, running from be- 
fore backwards, the whole length of which is deeply slit, but in 
such a way that its lips close tightly. The function of this organ 
is quite enigmatical, and nothing analogous to it is known in 
other Penai. 
XLILI.— Contributions to an Insect Fauna of the Amazon Valley. 
CoLrorTeRA : Lonercornes. By H. W. Barss, Esq. 
[Continued from p. 124.] 
Genus STErRAsToMA, Serv. 
Serville, Ann. Soc. Ent. Fr. iv. 24. 
This is a well-defined genus, not very closely allied to any of 
the preceding. Its nearest relationship seems to be with those 
species of Acanthoderes which have slender fore tibie, rounded 
anterior acetabula, and closed acetabular sutures, tricarinate 
thorax, and prominent centro-basal ridges continuing as smooth 
carne to the apex of the elytra. It differs, however, from 
Acanthoderes in the complex tuberculation of the sides of the 
thorax. Instead of a simple lateral conical tubercle or spine, as 
is usual in the Longicorn family, the thorax presents, on each 
side, an irregular prominence furnished with three tubercles. 
In some species this prominence is very strongly developed, and 
then two of the tubercles are carried to the apex, giving it a 
bifid appearance, the third remaining at the base beneath. All 
the species have, besides this tricuspid prominence, an acute 
tubercle on each side near the fore margin of the thorax ; and 
some present, in addition to this, a similar pomted wart on the 
side, some distance above it. The muzzle, although similar in 
shape to that of A. dzvitta, is considerably longer and more 
broadened anteriorly than in any species of Acanthoderes, and 
the fore angles are more strongly pronounced. The mandibles 
are long, very slightly bowed, and much flattened. The centro- 
basal ridges of the elytra are curved outwards and prolonged 
behind as more or less flexuous smooth keels to the apex. In 
the males of some species the basal joint of the antennz forms 
an irregular many-angled club, and is longer in proportion to 
the third than is the rule in the section to which the genus 
belongs. 
