1:22 A REVISION OF THE ASTACIDA. 
verge to form the short acumen, without lateral angle or spme. In other 
specimens there are lateral spines at the base of the acumen (var. fridens of 
Von Martens), and in an intermediate form the rostram is simply angulated 
instead of spinous at the base of the acumen. The sides may be more or 
less convergent from the base. In specimens from Mazatlan, the rostrum, 
although destitute of lateral spines, differs from the typical form in being 
longer and more tapering. The post-orbital ridges are in some specimens 
unarmed at the anterior end, in others they end in a sharp spine. The fore 
border of the carapace is angulated under the orbit. No branchiostegian 
spine. Carapace smooth, punctate on the gastric region and areola. No 
lateral spine. Areola of moderate width. Abdomen longer than the cephalo- 
thorax, broad, especially in the female. Anterior segment of telson armed 
on each side with one, two, or (seldom) three spines. Antennal scale broad. 
Chelipeds without spies or tubercles, excepting, in some specimens, one or 
two spicules at distal end of superior border of the meros; hand of male 
long, cylindrical, inflated ; fingers slender, with cutting edges smooth, meeting 
throughout their length. In the female the chela is shorter and broader. 
In the first form of the male the third segment of the second and third 
pairs of legs has a sharp hook, the first abdominal appendages are of mod- 
erate length, recurved, bifid, the rami divaricate, horny-tipped, the outer 
one ending in a slender recurved point, and furnished with a single seta 
on its posterior border, the inner one taterally compressed, spoon-shaped at 
the end. 
The second form of the male has the hooks on the second and third pairs 
of legs slightly developed, the first pair of abdominal appendages less deeply 
bifid, the tips of the rami membranous and both blunt. 
Annulus ventralis of the female movable, fixed only at the posterior end, 
between the sterna of the penultimate and the last thoracic somites. The 
ventral face of the annulus is marked by a longitudinal fossa open at the 
posterior end. 
Saussure’s types of C. Montezume in the Berlin Zodlogical Museum were 
examined in September, 1870, by Dr. Hagen, who has kindly furnished me 
with the following information concerning them. The types are in alcohol, 
male, form IL, and female. In the male (young) the rostrum is nearly 
rounded in front. Another jar contains male, form II., and female, also from 
Saussure, with tridentate rostrum. The second and third pairs of legs are 
hooked, as is stated by Saussure. 
