122 A REVISION OF THE ASTACID.E. 



verge to form the short acumen, without lateral angle or spine. In other 

 specimens there are lateral spines at the base of the acumen (var. tridens of 

 Yon Martens), and in an intermediate form the rostrum 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 spines 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 lias 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 laterally 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. Montezumce in the Berlin Zoological 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 I., 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. 



