114 Rev. T. R. R. Stebbing on Gastrosaccus spiniferus. 



Fig. 10. Transverse section through the head of the same form of pedi- 

 cellaria, cut slightly oblique : X 57. The letters have the same 

 signification as in tig. 9. 



Fir/. 11. A portion of the glandular sacculus of the valve, more highly 

 magnified : X 470. Letters same as in fig. 9. 



Fig. 12. Longitudinal section of the tactile cushion : x 235. Letters 

 same as in tig. 9. 



Fig. 13. Longitudinal section of the pedicellaria globifera of Echinus 

 melo : x 57. a, the glandular sac of the valve ; x, the secon- 

 dary mucus-sac. 



XIII. — Gastrosaccus spiniferus, Goes, newly described and 

 figured. By the Rev. T. R. R. Stebbing, M.A. 



[Plate III.] 



Family Mysidae. 



Genus Gastrosaccus, Norman. 



The animal is transparent, with dendritic markings on cer- 

 tain parts, in particular on the last pereion- and the first and 

 third pleon-segments, and a large patch on each side of the 

 marsupial pouch. From the eyes to the extremity of the tail 

 it is less than half an inch long. 



Between the eyes is a short, longitudinally grooved, blunt 

 rostrum, beneath which, and produced beyond it, is a pointed 

 frontal process ; from this to the cervical groove is about a 

 third of the dorsal, a fourth of the lateral, length of the cara- 

 pace. The large dorsal sinus of the carapace has its inner 

 part margined with eight spines directed backwards, slightly 

 converging, a little bent downwards at their tips ; the central 

 are the longest, the lateral very small ; behind them there is a 

 small slit in the margin, making a sort of spine-like lobe. 

 The first four pleon-segments are nearly cylindrical, some- 

 what compressed at the sides ; the last of the four ends 

 dorsally in a small keeled adpressed prolongation. The 

 fifth segment is dorsally carinate, the keel ending in a slightly 

 upturned membranous process of small size, convex, pointed 

 at the end ; its length once and a half its breadth at the base. 

 From the base of the pleon the body narrows rather rapidly 

 backwards to the end of the fifth segment ; from this 

 point the sixth segment slightly widens towards the telson ; 

 it is cylindrical, nearly equal in length to each of the 

 two segments preceding it; the second and third are the 

 shortest. 



