212 Bulletin, Vanderhilt Marine Museum, Vol. Ill 



moths), the larvae of which are popularly known as "measuring 

 worms. ' ' 



Type: "Inhabits salt water bays, common." Say referred to the 

 East Coast of the United States. Deposited in the Academy of Natural 

 Sciences, Philadelphia. 



Distribution: Known from the East Coast of the United States, 

 from New England to Florida. 



Material examined: 14 specimens, including both sexes, taken at 

 Eastport, Maine, August 23, 1923. 



Habits: This species lives in the sea-weeds, coralline mats and 

 hydroids, its thread-like body rendering it invisible among the waving 

 fronds. Occasionally a colony of hydroids becomes attached to a liv- 

 ing green turtle's shell, and the Caprellas adapt themselves to this sea- 

 going environment, apparently without difficulty, to judge by the 

 countless numbers of specimens in all stages of growth that I have 

 personally picked from the backs of a hundred or more turtles brought 

 into Key West and Miami by the fishermen for shipment to northern 

 markets. 



The animal uses its three hinder pairs of legs for clasping around 

 the stem of the seaweed. Although it moves nimbly, looping its body 

 along, after the meaner of "measuring worms," the amphipod will lie 

 quiescent for hours, its body attached to the weed by means of the 

 clasped three sets of hinder legs, the outer part of the body swinging 

 in the tide, like a bit of seaweed, the giant chela occasionally seizing 

 passing prey, not infrequently another Crustacean. 



According to Dr. S. I. Smith, these animals possess the power of 

 adapting their own color pattern to that of their environment, being 

 generally grey with darker specks, when living among the hydroids, 

 but often bright red when living among red algae. 



Technical description: Adult male: Figured, plate 80. Body 

 linear, irregularly subcylindrical, head obtuse anteriorly, with one 

 short, acute spine dorsally, gibbous beneath ; the first thoracic segment 

 is longer than the head but somewhat shorter than the three succes- 

 sive segments which are approximately subequal; the last three seg- 

 ments are successively shorter, the terminal one the shortest of the 

 series. The thoracic segments are rounded on the upper surface gib- 

 bous on the lower, and ornamented with a series of unevenly placed, 

 conical spines of varying sizes. 



The first legs are subchelate, much smaller than the larger second 

 pair, the propodus of which is enlarged, thickened, except along the 



