M Y S IDEA. 649 



CYRTOPIA DETRUNCATA. 



Carapax breviter rostratus (rostro oculis valde breviore), marginibus 

 integer, anticd posticeque angulis rotundatus. Segmentum abdominie 

 posticum lamellis amdalibus parce langius, apice truncatum et spinu- 

 lis minutis cequis armatum, barbis apicem non superantibus. 



Carapax short rostrate (beak being much shorter than the eyes), mar- 

 gin entire and angles before and behind rounded. Last abdominal 

 segment slightly longer than caudal lamellae, truncate at apex and 

 armed with minute equal spinules, subapical barb not extending 

 beyond apex of segment. 



Plate 43, fig. 3 a, animal, immature; b, eyes and inner antennae; c, 

 caudal extremity ; d, outer antennae ; e, extremity of mandible ; /, g, 

 maxillae ; h, antepenult leg ; i, penult leg ; k, posterior pair ; I, part 

 of liver. 



Piicific, off south end of Hopper Island, near the equator, in longi- 

 tude 173 east. Collected, at 4 A. M., April 16, 1841. 



Length, one-third of an inch. Colourless. Body slender. Carapax 

 deeply excavate behind. Inner pair of antennas with the base more 

 than twice as long as the eyes ; first joint longer than the two follow- 

 ing together ; the lower or outer apex of this joint prolonged nearly to 

 apex of following joint; second and third joints (or two last of base) 

 subequal. 



The mandibles appeared to have no palpus (but this requires farther 

 examination) ; they are dentated at apex, and have a stout molar pro- 

 cess on one side. Maxillae lamellar, as in figures /, g. 



As the animal was immature, there were but three pairs of legs very 

 distinct; the second and third had furcate branchiae at base; besides 

 these, there are two pairs of branchiae posterior to the legs, they were 

 small bi-digitate sacs, attached by a short pedicel of the same size. 

 The second pair of legs was the longest, and both the second and third 

 had a short branch or palpus, but not so developed as to be used as an 



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