M Y S I D E A. 



663 



cuspidate in front. Eyes long, obconical. Abdomen very slender. 

 Posterior segment truncate and armed with minute unequal spi- 

 nules. Thoracic feet twelve, two-branched, pediform branch four 

 or five-jointed, the other (or palpus) furnished with a few setae; 

 other four feet anterior to these quite small. Abdominal appen- 

 dages rudimentary. 



This species, as it swims, with its very slender body, its extended 

 legs, and thorax of peculiar form, has much the aspect of a skeleton, 

 the legs corresponding to the ribs. The front is acute and rather long 

 rostrate ; and either side there is a divaricate acute projection, shorter 

 than the beak. The neck is quite narrow in some species, being less 

 than half the greatest breadth of the thorax ; and sometimes there is 

 a stout spine on what may be called the shoulders. The penult 

 abdominal segment has a spine at apex, and the last segment is nearly 

 linear, with a truncate or excavate apex, and a regular arrangement 

 of spinules, one at either angle larger than the intermediate. The 

 caudal lamellae are very slender and short ciliate. The eyes are 

 rather long conical, with the summit rounded. The abdomen is ex- 

 tremely slender, the joints all oblong. The appendages are short and 

 naked. 



The inner antennae appear to be simple, few-jointed, but rather long. 

 The outer have a short base and two flagella. No basal scale was 

 observed. The joints of the flagella were quite long. 



The posterior pair of thoracic legs is the smallest. The preceding 

 five pairs are similar, and the last of them rather the longest. 



SCELETINA ARMATA. 



Carapax antich valde constrictus, cuspidibus lateralibus valde divaricatis 

 collo angusto et humeris spind crassd armatis. Segmenta abdominis 

 5 antica spind acuta infra utrinque armata, ultimo lineari, truncato. 

 Antennm interna? thorace paulido breviores, ^-articulator, cylindrical, 

 articulo ultimo longiore. 



Carapax with the neck-like constriction deep, making the neck narrow, 

 acute angles in front strongly divaricate, and shoulders back of 

 constriction armed with a stout spine. Five anterior abdominal 



