DECAPOD CRUSTACEANS OF THE WEST INDIES 75 



including 228 with eggs (cl 3.2-6.2 mm), and 295 juveniles (cl 1.1-1.9 

 mm). The smallest recognizable males, in which the appendix 

 masculina on the second pleopod varies from a bud to twice the length 

 of the appendix interna, have carapace lengths of 1.8 to 2.0 mm. 



Ecological notes. — Micratya poeyi has been observed in at least 

 two quite different habitats. In the rivers and smaller cascading 

 brooks, it frequents the riffle areas, where it is particularly abundant 

 among concentrations of small rocks and pebbles. It is also abundant 

 in rapidly flowing drainage ditches, among roots of shoreline plants 

 and plants trailing in the current. Among the features that these two 

 diverse types of habitats have in common are a swift current and a 

 place in which the animals may gain a foothold. 



In Mannet's Gutter (station 4), where an attempt was made to 

 coUect decapods by using pronox, M. poeyi seemed to be much more 

 sensitive to the poison than any of the other shrimps and crabs. 



Distribution. — West Indies and RepubHc of Costa Rica (?) 

 (Cuba, Jamaica, Puerto Rico, Dominica, Martinique). Like Jonga, 

 Micratya was thought to be confined to the West Indian islands 

 until a single ovigerous female was collected by D. P. Kelso in the 

 Rio Agua Fria (8 miles from sawmiU), Tortuguero, Costa Rica, 

 August 25, 1964. Specific determination of this specimen must remain 

 questionable until additional material becomes available from the 

 mainland, but there is no doubt of the genus. 



Dominica Stations: 1-4, 7, 13, 14, 17-19, 28, 30-33, 40, 44, 53-56, 

 59, 60, 63, 65, 66, 68, 69, 72, 74-80, 84, 85, 87, 88, 103, 105, 109 

 (0-1,350 ft.). 



Remarks. — In Dominican adults of this common little shrimp, 

 the number of dorsal teeth on the rostrum varies from 5 to 9. In the 

 smallest juveniles, with carapace lengths of 1.1 and 1.2 mm, there 

 may be only one or two barely distinguishable teeth, but the number 

 increases rapidly with growth. SHghtly larger juveniles usuaUy have 

 three or four rostral teeth, and the maximum number of nine can be 

 found at carapace lengths of 3.0 mm in males and 4.2 mm in females. 



The Dominican coUections indicate that aU three of the color pat- 

 terns described above are represented in every population. Examina- 

 tion of 87 specimens, some Hving and some preserved but stiU showing 

 the dark-adapted patterns, suggest that the majority of males (22) 

 belong to the form with vertical pale bands. Females (15) and juveniles 

 are often similarly banded, but females seem to be most prevalent 

 among the unhanded forms, either with (21) or without (15) the 

 light, mid-dorsal stripe. 



Inasmuch as females with eggs were coUected on Dominica in 

 January, February, March, May, and September, the species probably 

 breeds throughout the year. Larvae obtained from one of them after 



317-180—69 7 



