382 DE. W. T. OALMAN ON NEW OE EAEE 



Genus Diastylis. 



The genus Diastylis, as it stands at present, is hardly more than a convenient 

 receptacle for unclassified Diastylidse, and this alone can excuse the temporary 

 assignment to it of the remarkable form here described from immature specimens 

 as Diastylis (I) fistularis. The other new species is a typical Diastylis, or, rather, 

 it belongs to the group which we may assume to be typical until Say's D. arenaria is 

 rediscovered. 



Diastylis korsana, sp. n. (Plate XXXVII. tigs. 19-25.) 



Description of adult Female. — Total length 12 mm. 



Carapace about one-third of total length, its vertical height a little less than half its 

 length, widest behind, where the width is about two-thirds of its length ; dorsal surface 

 arched, slightly uneven in front and with a median depression posteriorly between the 

 branchial regions ; the whole surface beset with setse, among which are minute spini- 

 form points, most conspicuous on the anterior part of the dorsal surface. Pseudorostrum 

 slender, slightly curved as seen from the side, nearly one-third of total length of 

 carapace. Antennal notch obsolete, lower margin minutely dentate anteriorly. 

 Ocular lobe very small or absent ; no distinct eye. 



The free thoracic somites are rather less thickly setose than the carapace ; the last 

 thoracic somite has the posterior corners not produced, rounded, with a minute terminal 

 spinule. 



The abdomen is about as long as the cephalothoracic region ; the first five somites 

 have the lateral corners produced and spiniform, and each bears a pair of small dorso- 

 lateral teeth. 



The telson is as long as the last two somites together ; the post-anal part is a little 

 shorter and much narrower than the pre-anal, and bears on each side about ten long, 

 slender, almost setiform, lateral spines ; the terminal spines are a little stouter and, 

 like the lateral spines, curved upwards. 



The antennules are rather slender and the peduncle reaches to the tip of the 

 pseudorostrum ; the first and third segments are subequai and longer than the second ; 

 the flagella were imperfect in all the adult specimens examined. 



The first legs extend beyond the pseudorostrum by the length of their two distal 

 segments ; the basis is two-thirds as long as the distal segments together, and carries 

 numerous long plumose hairs ; there are a few small teeth on its lower surface ; the 

 propodus is longer than the carpus and nearly twice as long as the dactylus. 



The second legs have the basis a little shorter than the distal segments together, 

 carrying long plumose setse ; the carpus is longer by one-half than the propodus and 

 dactylus together. 



The last three pairs of legs are stout, with numerous strong setse on the distal 



