MUSEUM OF COMPARATIVE ZOOLOGY. 65 



stomach the intestine bends downward and forward, then takes a sudden turn 

 backward. The eyes are seated on two small projections of the front margin 

 of the head, not even by courtesy to be called tentacles. The foot is protruded 

 as on a sort of peduncle, the connection with the body being constricted. The 

 soft parts are white with traces of purple and yellow. The penis is recurved, 

 sickle-shaped, rounded, with a small conical projection at the side of the tip. 

 It is very large for the size of the animal. The other characters are much as 

 in A. concavus. The animal is very sluggish and in captivity will remain 

 partly protruded for forty-eight hours, apparently without stirring, though 

 perfectly healthy. On the shells are found in May small circular ovicapsules 

 adhering by the whole base and with a flat circular top like a lid a little 

 set in. They are about one mm. in diameter, and are probably the ovicapsules 

 of this species. 



Acus protextus Conrad extends from Hatteras to Texas in 2-50 fms. I 

 have not received it from the Antilles. The more distinctly reticulated 

 variety I suppose from the figures to be T. lutescens E. A. Smith. It has 

 been obtained in 2-20 fms., from Cape Fear, North Carolina, to the Gulf of 

 Mexico. 



Acus Rushii Dall was dredged in 8 fms. by Dr. W. H. Rush, TJ. S. N., five 

 miles off Cape Florida, at the southwestern extreme of the peninsula. With 

 its strongly marked flat spiral sculpture and brilliant whiteness, it is one of the 

 most marked of our small species. 



Three species only were collected by the Blake, but all of these appear to 

 be undescribed. 



Terebra (Acus ?) benthalis Dall. 



Plate XXIX. Fig. 6. 



Shell pale brown, fading to white near the apex, slender, acute, twelve- 

 whorled ; nucleus swollen, glassy, white, smooth, of a whorl and a half; suc- 

 ceeding whorls with a peripheral row of pointed tubercles, behind which the 

 whorl is smoothed off to the suture, while in front a rib proceeds from each 

 tubercle to the next suture. These are gradually modified from whorl to 

 whorl, by the increase in the number of ribs and their being crowded, and 

 their prolongation backward to the suture where they end in a second fainter 

 tubercle ; on the last whorl the tubercles have become little more than faint 

 swellings on parallel crowded riblets, which seem to have been ligatured be- 

 tween the two rows. The whole surface is finely spirally striate, the base is 

 rounded ; the canal short and much twisted, the mouth narrow, elongated, and 

 without callus. Max. Ion. of shell, 21.0; of last whorl, 8.2 ; max. lat. of shell, 

 4.5 mm. 



Habitat. Off Morro Light, Havana, in 100 to 400 fms. 



This shell has a deep-water aspect, and though the soft parts were not ob- 

 tained I have no doubt it lived at the depth from which it was dredged. 



VOL. XVIII. 5 



