THE NAUTILUS. 29 



this. Wild oysters are also found on ledges and boulders at 

 the half-tide mark along the entire river bank for a distance of 

 two miles. A few of these fail to survive the exposure in win- 

 ter but where Fucus fronds cover them completely and they are 

 not molested they often grow to six inches in length. In these 

 situations they are subjected to protracted low temperatures 

 during the winter months and a short season for the growth of 

 the "spat". The water temperature in the month of Septem- 

 ber drops to the vicinity of 15° C. by the 30th. In the middle 

 of October the temperature is down to 12° C. and by the middle 

 of November down to 8° C. The density of the water varies 

 between 1.015 and 1.0225. The " spat" first appeared, or per- 

 haps more correctly, were first discovered on the twelfth of Octo- 

 ber. At this time they were about 6.5 mm. in diameter. On No- 

 vember 23 they were again measured and were about 11.5 mm. 

 Notes and specimens taken at this time were only for idle curi- 

 osity and are not absolutely reliable. 



The only enemies beside man that I know of are the boring 

 sponge and Urosalpinx cinerea. Inquiry and repeated examina- 

 tion have failed to discover the presence of the starfish or any 

 of the commensal crabs and I believe they fail to ascend the 

 river as far as the Durham beds. The beds are entirely self- 

 propagating. No attention is ever paid to the need of the ' ' spat ' ' ; 

 and clean shells or stones for their attachment have never been 

 placed in the river. I have never heard of the oysters having 

 been taken for commercial purposes, but many are gathered for 

 "home consumption ". 



THE NEW MEXICAN EXPEDITION OF 1914— ASHMUNELLA. 



BY H. A. PILSBRY AND JAS. H. FERRISS. 



[^Continued from p. 16.] 



ASHMUNELLA TETRODON P. & F. 



In the type lot the diameter varies from 12.8 mm. with 5J 

 whorls to 15 mm. with 5^ whorls. This is the usual range of 

 variation in size. In stations 75 and 71 all are rather small, in 

 the former from 12 to 14 mm. — mostly about 13 mm., and at 



