JQ2 CRUSTACEA. 



are oblong, nearly naked, there being a few very minute setules at 

 apex ; on the joints, the most prominent setules are at the outer apex 

 of the penult joint at base. Legs very nearly naked; the fourth joint 

 very short; first pair shortest and stoutest, and well adapted for pre- 

 hension ; third pair longer than second. 



Idot^ea brevicauda. 



Angusti ovato-elliptica, /route truncate. Abdomen lath oblongum, postice 

 paululo angustius et truucatum, angulis prominulis medioque postico 

 apiculato. Oculi lateralis, oblongi, vix prominentes. Antennas in- 

 ternee parvulce, dimidio basis externarwm non longiores. Antennas ex- 

 ternal dbnidium corporis longitudine non superantes, flagello 9-10- 

 articulato, paulo longkrre qwam basis, articulis brevibus, fere nudis. 

 Pedes longitudine postice sensim paululo increscentes, nudiusculi. 



Narrow ovato-elliptic, truncate in front. Abdomen broad oblong, 

 posteriorly a little narrower and truncate behind, angles rounded 

 and a little prominent, at middle of posterior margin apiculate. 

 Eyes lateral, oblong, hardly prominent. Inner antennae small, not 

 longer than half the base of outer ; outer pair scarcely longer than 

 half the body, second joint short, with outer apex prominent, fla- 

 gellum nine to ten-jointed, rather longer than base, joints short, 

 nearly naked. Feet increase slightly from the first pair to the last, 

 nearly naked. 



Plate 46, fig. 4 a, animal, enlarged ; 4 b, part of flagellum of outer 

 antennae. 



Abundant in the harbour of Rio Janeiro. Taken, December 25, 

 1838. 



Length, one-half to three-fourths of an inch. Colour, brownish 

 gray. Body broadest at the third thoracic segment. The first tho- 

 racic segment is very short, except laterally, and receives the head ; 

 the third is a little the longest ; the sixth and seventh have the pos- 

 terior angles subacute, which in the others are rounded. The abdo- 

 men narrows posteriorly, very exactly in conformity with the thorax 



