Mr. H. J. Carter on a Siliceous Sand-8ponge. 15 



with an inflation, which is constricted in the middle and set 

 on at a right angle upon the principal stem, like the handle of 

 a walking-stick. The copulation of the Cyprides appears to 

 take place in the mud. M. Zenker has described, in the 

 females, two piriform sacs [receptacula seminis) in which the 

 spermatozoids are stored up ; these, according to him, com- 

 municate by two excretory canals with the oviducts. Accord- 

 ing to my observations, the canals in question simply open at 

 the base of the tail. 



Although the young Cyprides undergo no metamorphosis like 

 those of a great number of other Crustacea, I have found that 

 the form of the valves in the young of many species is the 

 opposite of that observed in the adults. 



Bosc and Straus succeeded in keeping Cyprides in wet mud 

 for a period of time which they do not particularize. I have 

 repeated the same experiment, and found that this time did 

 not exceed eight days, and that many other small aquatic ani- 

 mals, such as Cyclops^ Hydraclma^ Nais, and the larvae of 

 Diptera, possessed the same power of resisting for a long time 

 a nearly complete privation of water. 



V. — Descnption of a Siliceous Sand- Sponge found on the 

 South-east Coast of Arabia. By H. J. Carter, F.R.S. &c. 



Tethya dactyloidea (mihi). 



Mammilliforai, elongated, date-shaped, fixed, erect, fleshy, tough ; 

 surface smooth above, becoming hispid with recurved spines 

 below ; colour reddish brown, pui-plish. Upper extremity 

 obtuse, round, perforated at the point by a circular aperture 

 or vent separated into five divisions by as many septa ex- 

 tending from the circumference to a central union. Lower 

 extremity terminating in a bundle of loose, soft, spiculiferous, 

 keratose filaments, which, tending to a spiral arrangement, 

 finally spread out root-like into the sand beneath. Hollow 

 internally for the purpose of receiving the contents of the 

 excretory system of canals, which, ramifying through the 

 cortical fleshy body, thus empty themselves into the cloacal 

 cavity, somewhat constricted at the vent, already de- 

 scribed. Spicules fusiform, pointed at each end, or with 

 one extremity terminating in a trifid extension. Body of 

 sponge If inch long and | inch broad ; pedicel 1 inch long. 



Hob. Sea, south-east coast of Arabia, in shallow sandy bottom 

 near shore. 

 Ohs. This is a siliceous sponge growing erect on the sand, 



