67 



The rostrum is a fine acute upcurved spine, about a third of its length 

 lying beyond the eyes : its carina, which is continued backwards nearly to the 

 posterior border of the carapace and is a little concave at the cervical groove, is 

 fairly closely and evenly serrated in its whole length, the first serration, which is 

 situated on the rostrum itself, being larger than any of the others. 



In addition to the ridges present on the carapace in P. latirostris, a branch 

 marks off the upper limit of the posterior part of the branchial region. 



The spine in which the carina of the 4th abdominal tergum ends, though 

 not larger than that of P. latirostris, is more salient. 



The antennular scale is shorter than the basal joint of the peduncle. 



The external maxillipeds reach a little way beyond the antennal scale. 



The legs are almost exactly the same as those of P. latirostris, only the 2nd 

 pair are considerably more than half the length of body. 



In the largest specimen the length of the carapace is 26'5 millim. (the 

 rostrum contributing more than 5 millim.) and that of the abdomen is 37 millim. 



Andaman Sea 650 fathoms : Arabian Sea, north of the Laccadives, 696 

 fathoms. 



Regd. Nos. p (Type of the species) : . 



PSATHTROCAEIS, "Wood-Mason. 



Psathyrocaris, Wood-Mason, in Eep. Marine Survey of India, 1890-91, p. 19, and Ann. Mag. Nat. Hist., Feb. 

 1893, p. 168. 



Integuments extremely thin, appendages delicate and very fragile. 



Body moderately compressed : carapace of good length, produced to form a 

 normal, though short, rostrum. The orbital angle is sharp but there are no 

 spines on the carapace. Abdominal pleura deep and wide : telson acute. 



Eyes and eyestalks vertically compressed : a papilla on the inner edge of 

 the eyestalk : eyes not, or little, oblique. 



Antennular peduncle of fair length, its scale comparatively large. 

 Antennal scale rather broad. 



Mandibles with a large straight two-jointed palp. 



The 1st and 2nd maxillae and the 1st maxillipeds are perfectly normal in all 

 parts, the coxa and basis being well developed. The 2nd maxillipeds have a 

 7-jointed pediform endopodite the terminal joint of which is a normal dactylus, 

 a minute exopodite, an epipodite and a gill-plume. The external maxillipeds are 

 pediform and have a rudimentary exopodite and a small epipodite. 



The exopodites of the last four pairs of thoracic legs, like those of the first 

 five pairs of abdominal legs, are of extraordinary length. 



