280 



The arthrobranchise of somite IX are small and slender and are crushed up 

 against the bases of the 2nd maxillipeds to which, at first sight, they appear to 

 belong. 



Key to the Indian species of Ptychogaster. 



I. The first segment of the telson is not much more than half the antero- 

 posterior diameter of the second segment ... ... ... P. hendersoni. 



II. The antero-posterior diameter of the first segment of the telson is much 



more than half that of the second ... ... ... ... P. investigatoris. 



47. Ptychogaster Hendersoni, Alcock & Anderson. 



Ptychogaster hendersoni, Alcock and Anderson, Ann. Mag. Nat. Hist., Jan., 1899, p. 23. 

 Illustrations of the Zoology of the Investigator, Crustacea, Plate XLV. Fie. 2. 



Carapace (including rostrum) equal in length to the first six fully extended 

 abdominal terga, covered with spinules and spines, in which a definite serial 

 arrangement of the larger spines is hardly manifest. 



All the abdominal terga (telson excepted) and pleura bear spines : the first 

 tergum has a transverse spiny carina continuous with a similar carina on the 

 anterior edge of the second pleura ; the second has two such carina? ; the third 

 has a longitudinal row of spines at the junction with either pleura but is other- 

 wise smooth ; the fourth and fifth have two transverse series of spines, besides 

 an occasional spine on their posterior edge ; the sixth has numerous spines, in- 

 cluding three conspicuous transverse series. 



First segment of the telson not much more than half the length of, and 

 slightly broader than, the second. 



External maxillipeds unarmed, except for the fine teeth along the inner 

 edge of the ischium, hairy along inner edge, especially at distal end. 



Chelipeds and legs long, slender, and spiny ; in the female (male unknown) 

 the chelipeds are more than 2- times the length of the fully extended body and 

 nearly half as long again as the legs ; the first two pair of legs are nearly of one 

 length, but the third pair are the longest by nearly a dactylus, owing to 

 the elongation of their propodite, which is nearly five times as long as the 

 dactylus. 



A female from off the Travancore coast, 430 fathoms, is 30 millim. in 

 extreme length when fully extended, and has chelipeds 86 millim. long and the 

 third pair of legs 55 millim. long. 



Colour salmon-pink, eyes deeply pigmented. 



Regd. No. —■ (Type of the species). 



