CALYPTR^EID^E. Ill 



adhere. Often this immature state is continued to a late period ; 

 if permanent it would belong to the subgenus Dispotaea (Sa}^), 

 of Messrs. Adams. But normally the sides of the cup close in, 

 while its body becomes greatly swollen in front. This cup now 

 assumes the form which is alwa}*s characteristic of the species 

 under every modification of external growth ; being well rounded 

 in C. imbricatum, angular at the side in C. spinosum, and with 

 the sides flattened against each other in (7. radiatum. In C. 

 rude, the adolescent stage is very soon completed and the cup 

 is permanently detached from the side of the shell, forming a 

 veritable ' cup and saucer,' one too after the fashion so prevalent 

 in America, where the cup-handle has never been formed. It is 

 a remarkable fact in geographical distribution, that the forms 

 intricatum and rude, which are typical in the west tropical 

 fauna of Central America, reappear but very sparingly on the 

 Caribbean shores ; while C. spinosum, which is far more common, 

 more variable and more widely distributed being found (under 

 various names) from California to Chili has not yet been dis- 

 covered on the eatern side. 



" Again, the C. radiatum, which is the most delicately formed 

 of the whole group, confines itself to the equatorial western 

 seas, not having been found further north than the Panama dis- 

 trict. An extremely remarkable specimen of C. spinosum was 

 dredged by Mr. Cuming in comparatively deep water. The net 

 brought up a large stone with a small hole in it, on looking 

 down which Mr. Cuming perceived a number of spines, as 

 though a sea-urchin was lodging there. A blow of the hammer 

 discovered the existence of a large cavity within, communica- 

 ting with the external world only through this narrow opening. 

 In the hollow of this cavity lay the limpet, turned as it were 

 nearly inside out. The creature had gone to live there when 

 3 r onng, and being of sedentary habits, it had not occurred to 

 him that he might be imprisoned for life by his own corpulence, 

 else he would probably have made his escape before he had 

 grown too large. As it was, he grew larger and larger, and as 

 the walls of his prison rose up round him on every side, he was 

 obliged to flatten out his shell till it became a plate, instead of a 

 cone. At the same time, his body protruding into the hollow, 

 the cup protruded along with it till it stood considerably 



