and auricular. The protoconch (Fig. 4, A, PI. VIII) shows very clearly 

 its conversion from a coiled shell to the broad, pan-like shell of the 

 adult. At this early stage the shell resembles that of an adult Sigare- 

 tiis. Then the mantle pours out from its entire margin lines of accre- 

 tion, the columella of the early shell forming the base of the so-called 

 seat of the adult form. 



CREPIDULA P;.ANA Say 



PI. II. Fig. 5. Length 32mm. 



Head bi-lobed, lobes slightly rounded; foot square in front, sides 

 parallel, rounded behind; tentacles pointed, eyes on prominent bases. 



CREPIDULA CONVEXA Say 



PI. II. Fig. 6. Length 10mm. 



Head bi-lobed, lobes long; foot rounded, sharply auriculate; 

 tentacles long and blunt. The resemblance of the soft parts of the 

 three species of Crepidula to Crucibulum striatum is very marked. In 

 the latter species the lobes of the bifurcated head are larger than in 

 Crepidula. Figs. 5 (A) and 6 (A) PL 8, are believed to be the early 

 stages of C. plana and convexa. A curious wedge shaped process comes 

 in between the first coil of the shell and the upper part of the body 

 whorl in C. fornicata and plana; I did not observe it in C. convexa. 



CRUCIBULUM STRIATUM Say 



PI. II. Fig. 7. Length 22mm. 



This genus known as Calyptrea in Forbes and Hanley, Jeffreys, 

 and in the first edition of Gould's " Invertebrata," is not an uncommon 

 shell along the coast. Our shell is closely related to the English 

 species though the figure given of the English form of the animal 

 differs from the one here represented. The head is strongly bi-lobed, 

 the tentacles are thick and stout with enlargements at their bases on 

 the outside of which are the eyes. The foot varies in form, rounded 



