26 



STALK-EYED CRUSTACEA. 



tive forms which show distinct affinities with the Maioids, Cancroids, and 



Portunidae. 



Trachycarcinus corallinus Tax. 



Plate A. 



Bull. Mus. Comp. Zool., XXIV. 156, 1893. 



The carapace is of an irregularly pentagonal shape, the antero-lateral 

 borders being about twice the length of the postero-lateral ; the general 

 surface is densely clothed with a dark brown coat which under a lens is seen 

 to be made of a multitude of close-set club-shaped set£e ; when this coverinr«- 



is scraped off the shell appears smooth and white underneath. The various 

 regions of the carapace are well marked out by intervening furrows, and 

 from the more prominent parts of each region there arise groups of flattened 

 turbercles of ivory whiteness which stand out in striking contrast to the 

 sombre brown of the general surface of the carapace. These tubercles arc 

 arranged in groups or bunches, the principal of which are placed as follows : 

 two anterior lateral and one posterior median on the gastric region ; four 

 disposed in two pairs on the cardiac region ; five or six on each branchial 

 region ; and one, of a crescentic shape, on each hepatic region. Each group 

 of tubercles resembles the crown of a complex molar tooth whose cusps have 

 been worn down to a common level. The front is produced into three acute 

 teeth, the median twice as long as the lateral. The walls of the orbit 

 exhibit four teeth separated by deep hiatuses ; these teeth are a prtcocular, 

 supraocular, postocular, and subocular ; the pra)ocular tooth is compressed 

 and blunt, its anterior edge denticulate. Behind the postocular spine the 

 antero-lateral border of the carapace displays three prominent teeth, increas- 

 ing in length successively from before backward ; there is, too, a minute tooth 

 just back of the largest, posterior lateral tooth. The posterior margin of the 

 carapace is provided with small teeth and is concave at the middle part. 

 The eye-stalks are very slender, far from filling the orbits. The eyes them- 

 selves are not larger than the extremity of the eye-stalk ; they have an im- 

 perfectly faceted cornea, but show no trace of pigment. The basal segment 

 of the antenna is small and cylindrical ; it does not quite reach to the margin 

 of the front, and is not firmly soldered to the carapace ; the other two seg- 

 ments of the peduncle are longer and slenderer than the basal segment; the 

 end of the peduncle does not quite reach to the extremity of the rostrum; 

 all of the segments of the peduncle are furnished with long setce, while the 



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