100 OKHAMANDAL MARINE ZOOLOGY REPORT 



hidden in a dorsal view. Eyes small. Orbits cii'cular, eye-peduncles short. Antennae 

 minute and placed within the anterior hiatus of the orbit. 



Chelipedes smooth, the movable fingers being slightly hairy, and as long as 

 the palm. 



Ambulatory legs slender and increasing in size posteriorly, except the fourth pair, 

 which are smaller than the first pair. 



Dactyli of the third and fourth pairs one and a half times as long as those of the 

 first and second. 



Dactyli of the last pair, hairy at the tips. 



Abdomen seven-jointed, broadening considerably posteriorly. 



Length of carapace 9 mm., breadth 11 mm. 



Numerous females bearing eggs. Colour in formalin, dirty brownish red. 



MALE. Carapace smooth. Front broadly triangular, short, and raised. 

 Posterior, broad and sharply truncate. The oblique cervical grooves well marked and 

 terminating just external to the orbits. Eyes small and visible in a dorsal view. 

 Eye-peduncles very short. Antennules extremely minute. Antennae long with 

 peduncles backwardly projecting. 



Chelipedes similar, short, and equal in length to the breadth of the carapace. 

 Merus slightly longer than broad, with a rounded entire crest on its distal external 

 face. Carpus slightly longer than broad, and curiously curved. Propodite longer than 

 carpus, dactylopodite almost as broad as long and somewhat flattened. Fingers curved 

 with a hiatus between them when closed, and hairy on their opposing surfaces. 

 Succeeding legs slender. First pair approximately equal in length to the chelipedes, 

 second pair longer than the first pair by slightly more than a dactylus, third pair 

 longer than second pair by a dactylus. 



Abdomen narrow, permanently flexed under the body, and narrowing posteriorly. 

 First pair of abdominal appendages modified into long, cylindrical, rod-like bodies 

 which project from beneath the abdomen. 



Length of carapace 7 '5 mm., breadth 9 "5 to 10 mm. 



Apart from sexual characteristics, the male differs markedly from the female 

 in (1) its much smaller size and (2) the form of the rostrum. 



Pinnoteres placuncB is characterised by being extremely flattened dorso-ventrally, 

 by having the front of the carapace straight and broad in the female, and by the 

 somewhat squarish outline of the carapace. 



Habitat. Commensal within the mantle cavity of Placuna placenta, Balapur 

 and Rann Bays in the Gulf of Kutch, India ; abundant. 



Rare in the same species of Lamellibranch in Tampalakam Bay, near Trincomalee, 

 Ceylon, one to three fathoms. 



Out of twenty adult Placuuse examined alive and hailing from Balapur Bay, Beyt 

 Island, in the Gulf of Kutch, one shell only was without any pea-crab commensal. 



