DECAPOD CRUSTACEANS OF THE WEST INDIES 83 



third abdominal somites each with narrow transverse band posteri- 

 orly, neither band approaching bases of plem'a. Dorsolateral portions 

 of second through base of sixth terga with longitudinal stripe of 

 red chromatophores; two similar ones present on pleiiron of first 

 abdominal somite, one along base of pleuron and other at level of 

 postero ventral bluish-purple stripe on branchial region; lower row 

 on pleuron followed on succeeding three pleura and on sixth somite 

 by narrow longitudinal row of white chromatophores; lower margins 

 of second, fom"th, and anterior portion of fifth pleura with row of 

 white chromatophores; bluish-purple stripe present immediately 

 above marginal row of white chromatophores on fourth and fifth 

 pleura, and another slightly dorsal to latter bluish-pm-ple stripe 

 on third and posterior portion of second pleura. Articular knobs 

 with purple spots at anterior margins of second, third, fifth, and sixth 

 somites. Posterolateral portion of sixth somite with irregular brown 

 spot and brownish-purple one at dorsal base of lateral spine. Telson 

 and uropods with brown margins, purple spots at articular knobs, 

 and outer ramus of uropod with distal yellow area. 



Lower portion of antennular peduncle and inner flagellum blue; 

 antennal peduncle and scale with blue markings. Pereiopods trans- 

 lucent with orange at bases of fingers of first and second, and at 

 bases of three distal podomeres on remaiiung pereiopods. Pleopods 

 with blue spot on posterodistal end of protopodite and blue line on 

 exopodite. 



Material examined. — The Dominican collections contain 212 

 males (carapace lengths 3.8-9.9 mm), 204 females (cl 4.0-12.5 mm), 

 including 1 \vith eggs (cl 10.9 mm), and 1,457 juveniles (cl 2.0-3.9 

 mm). The appendix masculina on the second pleopod of the male 

 may not become apparent in this species until a carapace length of 

 nearly 7.0 mm is attained (it is a minute bud in two specimens with 

 carapace lengths of 6.1 and 6.2 mm), but the asymmetrical form of the 

 endopod of the first male pleopod is usually noticeable at carapace 

 lengths of between 4.0 and 5.0 mm, and it is discernible in one specimen 

 with a carapace length of only 3.8 mm; a carapace length of 4.0 mm 

 was therefore used as the minimum size at which sex can usually be 

 determined. 



Ecological notes. — Xiphocaris elongata occurs in many diverse 

 types of habitat on Dominica, but it is not everywhere abundant, 

 and just what factors determine its absence or presence are not known. 

 Fully mature specimens were collected, usually from pools, in the 

 upper reaches of streams at altitudes of 200 to 900 feet, where no 

 juvenile specimens were encountered. Within the pools, groups of 

 individual shrimps clung to submerged rocks, frequently on those 

 exposed to full sunlight. In the Laurent River (station 48), on the 



