1908.] NATURAL SCIENCES OF PHILADELPHIA. 5 



At Woods Hole Sycotypus and F. carica were found only at places 

 where Ensis (razor clams) were abundant. I could not find them 

 on any other beach. Although I did not observe Sycotypus eating 

 Ensis, I think there is every reason to suppose that they do. 



The experiments on the amount of food are too few to be definite. 

 The results, such as they are, are expressed in Table II. (x) indicates 

 present but not eaten, (o) indicates not present. 



Table II. 



No. Conch. Days. Ostrea. Mya. Venus. Mytilus. Modiola. 



4 Sycotypus 10 x 13 x 7 x 



4 F. carica 10 x x 2 3 1 



3 F. perversa 42 7 



4 F. carica 42 



2 Sycotypus 42 4 



1 Sycotypus 2 4 



Very often one individual would eat a couple of clams or 03"sters in a 

 day, but as a rule the meals were far apart. 



Notwithstanding most persons' "impressions," it is highly improbable 

 that these mollusks ever bore through Lamellibranch shells. I have 

 never seen a hole that would fit their proboscis, nor does the wearing 

 of the teeth on the odontophore indicate that they were worn down 

 against a hard substance. Plate I, figs. 3-4 show the median tooth 

 of Urosalphinx which bores rapidly through the shells of mussels. The 

 former shows a tooth before being worn and the latter a tooth worn 

 down. These teeth compared with a similar series, Plate I, figs. 1 and 

 2, showing F. carica, suggest that there are two methods of wear. In 

 Urosalphinx the teeth are worn evenly off so that a straight line will 

 join the tops. The large teeth are worn level with the short ones. In 

 Fidgiir, however, the teeth are broken off in almost any way. Exami- 

 nations of the radulse of Nassa ohsoleta, Nassa trivittata, Lunatia and 

 Purpura lapillus seem to substantiate the view. But with the excep- 

 tion of Purpura and perhaps Nassa ohsoleta, too little is known how 

 they take their food to render any general conclusions tenable. In the 

 case of these last two, Purpura, which has a radula worn like Urosal- 

 phinx, has been observed to bore (Wilcox, 1905) ; and A^assa, with wear 

 such as I have described for Fulgur, has never been seen to bore, but 

 will crawl between the valves of Mya, wedging the valves apart, and 

 devour the flesh (Dimon, 1905). 



The other method of attack (I.ngersoll, 1884) is by breaking the 

 shell. As described by Ingersoll this is utterly impossible. However, 



