238 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



Acteon (Microglyphis) estuarinus Dall, n. sp. 



Shell small, white, plump, with a very short, rather acute spire, and swollen 

 last whorl ; there are four and a half closely coiled whorls, the uucleus being sinis- 

 tral and sunken; when fresh, tlie shell is of a translucent pinkish white, the 

 thicker parts near the suture are more opaque and give the effect of a white band 

 in front of the suture ; the general form resembles that of A. {M.) curtulus, 

 though the shell, with the same number of whorls, is much larger, the spire less 

 evenly dome-like, and the nucleus more sunken ; suture very distinct, almost chan- 

 nelled ; sculpture of flue, close-set, minutely punctate spiral lines, hardly visible 

 without a lens ; aperture with a well-marked anterior sulcus or canal; anterior 

 plait on the pillar strong, prominent, the posterior plait weaker, and ending fur- 

 ther within the aperture, but quite distinct. A very thin wash of callus on the 

 body; outer lip thin, simple. Alt., 5.5; diam., 3.7; spire above the last whorl, 

 1.0 mm. 



U. S. S. " Albatross," station 3194, off Estero Bay, California (N. Lat. 35° 

 23' 30"), in 92 fathoms sand, bottom temperature 45°.9 F. 



It may be accidental, but two living specimens were both without the opercu- 

 lum, which is present in the littoral species of Acteon. The species of Microgly- 

 phis at present known are : 



The temperature of the water in which they lived was 37° to 48° P., and the 

 bottom either sandy or muddy. 



Scapha ndridae. 



SCAPIIAI\{DER Mo.NTFORT. 



Scaphander Montfort, Conch. Syst., 1810, 2, p. 334, type Bulla lignaria Linne. 

 Assula Schumacher, Essai, 1817, pp. 78, 258. 



Tlie species of this genus are readily recognized, but the smaller forms belong- 

 ing to the family are often so similar to Acteocina (Gray, 1S47, type Actaeon 

 icetherilli Lea, better known as Tomatina A. Adams, 1S50) tliat in the absence 

 of the soft parts tlie reference of the shell to a particular group must be regarded 

 as merely provisional. 



The nomenclature of the groups is also in an uncertain sUtc, its final arrange- 

 ment depending upon the anatomical characters as yet unknown. If we must 



» See Plate 15, figure 12. 



