8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



Cotypes, U.S.N.M. No. 80450 from Nobska Beach, Mass., have 

 been deposited in the United States National Museum, 



Larval stages. — A few specimens of five different larval stages 

 were found. For convenience in making comparisons, these larvae 

 have been arbitrarily numbered i, 2, 3, 4, and 5 in order of their 

 increasing size, complexity, and maturity. All have two pairs of 

 antennae, mandibles, labrum, second maxillae, and caudal rami. Only 

 the two largest stages have first maxillae and maxillipeds, although 

 all five stages have a maxilliped segment (postcephalosome). 



Except for the second antennae and mandibles, all of the larval 

 appendages are strikingly similar to the corresponding appendages 

 of the adult. Attached to the basipod of the second antenna, and more 

 median than the base of the endopod, is an unsegmented biramous 

 quasi palp in all larval stages. The undivided basal portion of this 

 quasi palp is very short while the two rami are about as long as the 

 adjacent endopod (see pi. 2, fig. 8). The distal half of the outer 

 ramus and the distal third of the inner ramus consist of two setae 

 of similar length. In addition, the outer ramus has two small setae 

 near its base. Also, the endopod of the larval second antenna has 

 four segments while that of the adult has five. 



The presence of the unique quasi palp on the larval second antennae 

 suggests interesting conjectures. Although the quasi palp is not a 

 very well-developed or robust structure, it is possible that it may 

 function, or at one time did function, as a clasping organ. The 

 possibility then arises as to whether the fifth larval stage may be 

 (or may have been in the past) a functional male phase as is the 

 case in certain other protandrous Crustacea, Mollusca, and Nematoda. 

 In none of the fifth larval stages, however, could any internal repro- 

 ductive structures be discerned. 



The endopod of the larval mandible also dift'ers markedly from 

 that of the adult. In the former it is composed of three broad seg- 

 ments, the terminal segment being much smaller than the other two. 

 In the adult this ramus is composed of two long narrow segments. 



The smallest larvae found have a total of only 3 segments posterior 

 to the postcephalosome; the second smallest stage has 5 such seg- 

 ments; the next largest has 7; the other two have 10, the same as 

 the adults. No thoracic appendages are present on the first three 

 larval stages, but the fourth and fifth stages have 3 and 4 thoracic 

 appendages, respectively. In all immature stages the posterior part 

 of the cephalic shield, the postcephalosome, and all posterior seg- 

 ments except the last segment have chitinized troughs. 



