WOOD. PEYLOGESY OF CERTAIN CERITHIIDJE H 



effigiem omittere noluimus, quauiiiius huiusmodi alias differentias habeamus, 

 colore oiiiero orbitas depressiorllms. uiagis deusis luinutisque tuberculis asperas. 



While this description is meager, it is sufificient, with the aid of the 

 figure, for the identification of the species designated. The character- 

 ization of the shell as a small one excludes Cerithium nodulosum, with 

 which it has been confused. The reference to the margin of the mouth 

 as raised above the canal and resting upon it is like C. tuberosum and 

 unlike C. adansoni. The figure also resembles C. tuberosum in its high 

 spire, in the character of the aperture and of the ornamentation, so far as 

 this is indicated by the imperfect figure. 



Description of Cerithium Hby Bruguiere : 



Genre de eoquilles univalves, luiiluculaire, h spire reguliere, qui a pour 

 oaractere, 



Une coquille turrieulee, I'ouverture obli(iue, terminee k la base par un canal 

 etroit, totalement recourbe, ou moyennement recourbe, ou droit et tres-court, 

 mais jamais echancre. 



Genotype selected by Lamarck, 1799, Murex aluco Linne; 1801, 

 Cerithium nodulosum Bruguiere. 



The protoconch of the genus Cerithium has been observed in many 

 species and is found to be uniform in character. It forms a low, regu- 

 lar spiral of usually about one and one-half volutions. The limits of the 

 protoconch are not sharply defined, as the ornament begins faintly at 

 first and becomes gradually stronger, but for convenience the protoconch 

 has been assumed to end where the first traces of ornament appear. Prac- 

 tically the only difference found in the earliest whorls of the species 

 studied is in the extent of the smooth portion of the shell, which varies 

 from one and one-fourth to one and one-half volutions. This is due to 

 difference in degree of acceleration, the more accelerated forms having 

 the ornamentation crowded back to an early stage in shell growth. 



The surface ornamentation of Cerithium consists of spirals, ribs and 

 nodes, the great diversity observable in the ornamentation of the different 

 species being due to the relative development which each of these feat- 

 ures attains. In forms sufficiently retarded to show the order of intro- 

 duction of the various features of the ornamentation, it appears to begin 

 as one spiral, or in accelerated forms as more than one, additional spirals 

 coming in above the first. Eibs next appear and nodes are formed by 

 the concentration of material where the ribs and spirals cross. In a few 

 cases ribs appear after the first and before the formation of a second 

 spiral, but in no case have ribs been observed before the appearance of at 

 least one spiral. Intercalated spirals may come in either before or after 



