NO. 1593. 



ON LEIDYA DISTORTA— RICHARDSON. 



25 



overlap each other on the ventral side, completely inclosing the 

 marsupial cavity. The seven pairs of legs are small and feeble, the 

 propodus and dactylus forming a prehensile hand. a (See fig. 3.) 



The six segments of the abdomen are more or less coalesced in the 

 middle of the dorsal surface. The lateral parts of 

 each of the first five segments are produced into an 

 elongate double-branched pinnate appendage on 

 either side, so that altogether there are five pairs or 

 ten pinnate appendages to the first five segments. 

 The upper branches probably represent the pleural 

 lamellae and the lower branches the pleopods, so that, torta. leg of 

 in this interpretation, there are five pairs of single- ™™ PEMALE - 

 branched pleopoda and five pairs of single-branched 

 pleural lamellae. The sixth or terminal segment is furnished with 

 a single pair of elongated pinnate appendages, the uropoda. 



Description of young female. — The young female differs from the 

 adult in its narrower and elongated form, in not having the thorax so 



a b 

 Fig. 4.— Leidya distorta. Young female, a, dorsal view; b, ventral view. 



greatly distended, in the more equal length of the segments of the 

 thorax, which do not have the median dorsal plate as in the adult, in 

 having the segments of the abdomen more distinctly separated and 

 the lateral appendages more elongated. 



a Leidy mistook the prehensile hand for the " recurved, abortive hooklet." In 

 some positions the hand has the appearance of a blunt hook and the dactylus 

 is difficult to see. Leidy's figure is inaccurate and misleading. The article 

 immediately preceding the " hooklet," in Leidy's figure, is probably the carpus 

 and the merus combined. The line of separation between the two articles is 

 somewhat difficult to see. Another interpretation might be given to Leidy's 

 figure, the " hooklet " being the dactylus, the article preceding it, the propodus, 

 and the one preceding that, the combined carpus, merus, and ischium. 



