ACADEMY OF SCIENCES. r >7 



Phyllodurus abdominalis. Siimpson. 



When Stimpson, in his Crustacean and Echinodermata of the Pacific Shore 

 of N. A., page 71, first described this species, the female only was known to 

 him. This female, like all those belonging to the family Bopyridaz, is of com- 

 paratively large size, broad and clumsy in appearance, and lives attached to 

 another crustacean. 



The crustacean frequented by this commensal is Gebia ■pwjcttensis, a marine 

 crayfish common on these shores. 



About April 24th, I gathered a great number of Gebias in Tomales Bay, and 

 found that most of them, all except the largest specimens, had a female P. 

 abdominalis attached to one of the abdominal pairs of feet, to which it clung 

 closely by means of its hooked claws. 



A close inspection revealed, beside or near the large female, a small and 

 slender male, a kind of miniature edition of its stout mate. 



Never more than a single pair were ever found attached to one Gebia, but 

 the males appeared so regularly to accompany the females, that I believe that 

 in the few cases I did not find them, it was because they had dropped off in 

 handling the specimens. 



The males do not live attached to the Gebia, but are free to rove, and their 

 constant presence at .this season by the side of the females proves that this 

 is their season of love. 



■Male. Head semi-circular anteriorly, closely united to the succeeding seg- 

 ment. Third and fourth thoracic segments widest. Body oblong, boat-shaped, 

 tapering slowly from the fourth tp the seventh thoracic segment. 



Outer antenna? four-jointed; inner very small, reaching about to the middle 

 of the second segment of the outer.  



Eyes too small to be distinguished by a Coddington lens. 



First abdominal segment a little narrower than last thoracic, but flat; suc- 

 ceeding segments tapering rapidly to the sixth or telson, which is pointed at 

 the end, and is provided on each side with a small lamella, giving the whole 

 telson somewhat the appearance of a spear-head. " 



The lateral laminre of the first five abdominal segments round in sections 

 instead of segmental, as in the female, and considerably longer than the width 

 of the segments to which they are attached. 



The President referred to a letter on the subject of irrigation 

 sent to him by P. J. Flynn, and explained some of the errors 

 into which he had been led. 



The President read a continuation of his paper on Irrigation 

 in India, Egypt and Italy. 



