12 BULLETIN 201, UNITED STATES NATIONAL MUSEUM 



interpret the maxilla as composed of a 3- jointed protopodite on which 

 an endopod and exopod are borne on the third joint or basis the 

 appendage is brought into morphological line with the thoracic ap- 

 pendages. Similarly the maxillule can be interpreted as representing 

 only the protopodite of the limb with well-marked lobes on the pre- 

 coxal and basal joints. A 3-jointed protopodite to the antenna is 

 generally accepted. 



Order MYSIDACEA 



Pericarida which retain more or less completely the primitive 

 caridoid facies; the carapace extends over the greater part of the 

 thoracic region but does not coalesce dorsally with more than three 

 of the thoracic somites ; the eyes, when present, are movably pedun- 

 culate; the antennules are biramous; the antennae usually have a 

 large scalelike exopodite; the thoracic limbs (except sometimes the 

 first, second, and eighth pairs) have natatory exopodites; the first 

 and sometimes also the second pair are modified as maxillipeds; a 

 lamellar epipodite is present on the first pair; ramified branchiae 

 may be attached close to the bases of the thoracic limbs ; the pleopods 

 are often reduced; the uropods are lamellar forming a tail fan; the 

 young leave the brood pouch provided with all the appendages of 

 the adult. 



Hansen (1925) regards the branchiae of the Lophogastrida as borne 

 on the precoxal joint, therefore prae-epipodial in nature. This inter- 

 pretation of the branchiae means that they are podobranchs and not 

 arthrobranchs, as was supposed by Sars. 



Suborder Lophogastrida 



Segments of the thorax all well defined dorsally; first pair of 

 thoracic limbs developed as maxillipeds, robust ; exopodite imperfectly 

 developed or absent; epipodite very large, projecting within the 

 branchial chamber ; well-developed ramified branchiae present on the 

 second to the seventh thoracic limbs, rudimentary or absent on the 

 eighth pair; seven pairs of oostegites in the female; pleopods well 

 developed, biramous, natatory in both sexes, none modified in the 

 male ; no statocyst on the inner uropod. 



Family LOPHOGASTRIDAE G. 0. Sars 



Carapace large, more or less calcareous; second pair of thoracic 

 limbs developed as gnathopods; third to eighth pairs of thoracic limbs 

 developed as normal pereiopods, not chelate. 



There are five genera in this family, Lophogaster, Paralophogaster, 

 Ceratolepis, Chalaraspidum, and Gnathophausia. All but Cera- 

 tolepis are represented in the National Museum collection. 



