1922.] W. M. Tatters all : Indian Mysidacea. 489 



longer than any of the others, tarsus two-jointed, nail prominent. 

 Eighth thoracic limbs much reduced in size, shorter than the 

 exopod and slender. Telson a very short broad triangular plate, not 

 covering the statocyst, unarmed. Uropods short, robust, subequal, 

 without spines, statocyst large. First, second, third and fifth pleo- 

 pods of the male small unjointed plates, fourth pleopod of the 

 male consisting of a basal joint from which the exopod andendopod 

 are imperfectly separated, a small one-jointed endopod and a 

 large exopod, apparently consisting of a single joint terminated 

 by a single long stout seta, as long as the joint and imperfectly 

 annulose at the tip, the whole appendage reaching to the tip of 

 the uropods. 



Type: — Idomysis inermis, sp. nov. 



Remarks. — This curious genus is quite unlike any other Mysid 

 known to me. Its robust gibbous body and the set of the telson 

 and uropods remind one of Mysidopsis gibbosa, superficially, but 

 it is widely removed from that species in structure. It belongs 

 to the tribe Mysini and apparently to Zimmer's group III B. It 

 is abundantly characterized by the very short and broad antennal 

 scale and by the short unarmed telson. 



Idiomysls inermis, sp. nov. 



Text-figs. 23a-/, 2^a-g. > 



Locality. — Kilakarai, Gulf of Manaar, among weeds, 0-2 

 fathoms, February, 1913. One adult male, 4 mm. (Type ) 



Description. — Body robust, gibbous, abdomen flexed between 

 the third and fourth somites; carapace leaving the last thoracic 

 somite exposed, produced in front into a prominent triangular fron- 

 tal plate with a broadly rounded apex which reaches forward to the 

 distal end of the first joint of the antennular peduncle. 



Eyes very large, cornea much broader than the stalk, pigment 

 golden brown. 



Antennal scale barely outreaching the short antennular pe- 

 duncle, very short and broad, one and a half times as long as broad, 

 outer margin without setae and without a prominent distal spine, 

 terminal lobe broader than long, without a suture, no spine on 

 the outer distal corner of the joint from which the scale springs ; 

 peduncle of the antenna shorter than the scale and composed of 

 three short broad ?ubequal joints. 



Mandible with a well-developed cutting edge and molar 

 process, second joint of the palp broad. First maxilla with the 

 inner plate reduced in size and tipped by four or five feeble setae. 



Second maxilla with the outer plate very much reduced in 

 size and feebly armed with five small setae, second joint of the 

 palp linear, not expanded at the apex. 



First thoracic linib (first gnathopod) with a masticatory lobe, 

 tipped by two or three setae, on the second joint, no lobes on the 

 third and fourth; nail not more prominent than the other setae 

 arming the distal joint. 



