234 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.42. 



Respiratory tracts of peculiar shape, as shown in figure 5, the 

 smaller tract a perfect circle, 1 mm. in diameter, set into the inner 

 side of the larger one; the latter made up of an anterior circular area 

 the same size as the small area, a narrow neck around the latter, and 

 an elongate posterior portion, abruptly widened into a triangle with 

 rounded corners and with a triangular incision on its anterior margin 

 just behind the small area. 



Abdomen broadly ovate, one-half the length of the carapace, the 

 base projecting forward as a broadly rounded lobe on either side of 

 the last thorax segment, so as almost to meet the carapace lobes ; . 

 anal sinus triangular, four-sevenths the length of the abdomen, with 

 triangular and acuminate lobes; papillae lateral, at the center of the 

 sides of the sinus, linear and each tipped with three small setse. 



Sucking disks, each one-fourth the width of the carapace, situated 

 far forward and so close together that their inner margins almost 

 touch; supporting rays of the margin made up of a series of oblong 

 rods placed end to end and diminishing regularly and rapidly in size 

 outward (see fig. 6) . 



There are two small tactile papillae just behind the opening of the 

 oviduct, their convex sides touching on the midline, their anterior 

 ends enlarged into circular pads. 



Antennae of medium size, the first pair with comparatively small 

 claws on the basal joint, the three terminal joints very slender and 

 scarcely reaching beyond the tip of the basal joint; second pair 

 long and slender, armed with only a few minute spines on the two 

 terminal joints, but with a large and sharp spine just behind the base 

 of the proximal joint. Maxillipeds stout, the terminal joint small 

 and tipped with three tiny claws, the third joint with a broad lamellar 

 process on its ventral surface near the proximal end, the basal joint 

 with a triangular plate, whose two outer teeth are close together 

 and at some distance from the inner one, all the teeth of medium 

 length and acuminate. 



There are two pairs of accessory spines close to the midline opposite 

 the bases of the maxillipeds. All four pairs of swimming legs are 

 furnished with flagella, and the bases of the fourth legs are pro- 

 duced into boot-like tactile processes not quite reaching the lateral 

 margins of the abdomen. The mouth-tube is long and narrow with 

 the opening on the ventral surface and singularly square in outline. 



Male. — General shape similar to that of the female, but the anterior 

 margin of the cephaHc area projects much more strongly, the lateral 

 lobes of the carapace are much longer, overlapping the abdomen 

 considerably and leaving a much narrower posterior sinus. The 

 anterior corners of the abdomen are produced into narrow knobs or 

 processes, extending forward and outward. In the accessory sexual 

 organs the basal joints of the first legs are produced backward and 



