1869.] 141 [Perkins. 



MKASUBEMENTS. 



Length of shell 3 mill. Breadth 2.4 mill. Height 2 mill. 



" animal 58 " 



vent, siphon 3.6 " j from points f separation. 

 " dorsal " 2 " ) 

 " pallets 2 " 



The Teredos, in the wreck just mentioned did not, as all authors 

 that I have seen state, follow the grain of the wood alone in making 

 their tubes, but quite as often crossed it; and in some parts there 

 were more tubes running across the grain than with it, and, in gen- 

 eral, no regard seemed to be paid to this point. One day, about the 

 middle of May, as I was examining one of the animals under a lens, I 

 noticed a series of pellets, barely visible to the naked eye, coming 

 rapidly from the anal siphon. By the aid of a higher power I found 

 them to be embryos, ova and young, in all stages of development. 

 The ova were spherical, or nearly so. The mature embryos were 

 round, much flattened trans verely, a little flattened on one side, and 

 on the opposite furnished with a crescent-shaped portion which bore 

 a few rather long cilia, by which a brisk motion was effected. The 

 embryos were provided with cilia when quite immature, and even in 

 the ova there was a slow motion, though I could detect no cilia. 



The immature embryos were of all shapes and sizes, and contin- 

 ually changed their form, though usually one end was larger than the 

 other, and in all cases they were longer and narrower than when 

 fully developed. It may not be the habit of the animal thus to eject 

 eggs and embryos of all degrees of maturity. The specimen ob- 

 served was somewhat injured, and on this account may have been 

 excited to unnatural exertions. The animal seems to live about as 

 well, for a time at least, without the shell and parts contained as 

 with it. I have kept them living for many days after the body had 

 broken off just behind the shell, which it does very easily. 



Xylotrya palmulata Chenu, Man. Conch., Vol. ii, p. 11, figs. 

 64, 65, 66; Woodward, Man. Moll., p. 507, pi. xxiii, fig. 28; Stimps., 

 Check List. Teredo palmulata et bipalmulata Lamarck, An. sans 

 Vert., Vol. VI, p. 38. 



A few specimens of this shell were found with Teredo navalis. 



