1897.] NEW YORK ACADEMY OF SCIENCES. 807 



J. H. McGregor, " The Formation of the Spermatozoa in 

 Amphiuraa." 



F. E. Lloyd, " On the Mechanisms in certain boring Lamelli. 

 branch Molluscs." 



At the conclusion of the papers, there being no further busi- 

 ness, the Academy adjourned. 



J. F. Kemp, 

 Secretary. 

 C. L. Bristol, 

 Secretary of Section. 



[Paget Sound Zoology, Columbia University Contributions No. 5. ] 



ON THE MECHANISMS IN CERTAIN LAMELLI- 

 BRANCH BORING MOLLUSCS. 



By Francis Ernest Lloyd. 



[Plates XXV. and XXVI.] 



A short account of certain peculiar structural changes under- 

 gone by Pholadidea has already been given. ( In foot-note. 

 Science, Vol. XIV., No. 85, 1896.; The object of this paper is 

 to extend that account and to discuss the correlated structures 

 in certain allied forms. The forms, which have been studied 

 in addition to Pholadidea penita, are Zirphsea crispata, Para- 

 pholas, Teredo and Adula Jalcata. These forms occur on the 

 Oregon and Washington coast and on the shores of Puget 

 Sound, though they are not confined to these regions alone. 



Zirphdea crispata is found digging into the blue clay (till) to 

 a depth of 40-50 cm. Large specimens measuring 30 cm. were 

 found just north of Point Wilson. These forms are capable of 

 stretching their siphons enormously, so that, while the shell is 

 but 8 cm. long, they are able to reach to the surface from the 

 above named depth. The holes which they make into the tena- 

 cious till are found to be quite roomy, and the elbow room, so to 

 speak, is taken up by fine black silt and sand. As the siphonal 

 openings indicate, the clam does not maintain a constant posi- 

 tion with reference to the open waters as in the case of the razor 

 clam (Siliqua). The latter is always so placed that the dorsal 

 or exhalent aperture is nearer the sea and this I have observed 

 to be true even when it occurs on bars near the mouths of bavs. 



