308 BULLETIN OF THE 



shell described by D'Orbigny as T. rugosa " Conrad," but which Conrad had 

 never described. I have not seen D'Orbigny's figure. 



Thracia phaseolina Kiener. 



(?) Thracia phaseolina, Kiener, Dall, Bull. M. C. Z., IX. p. 110, 1881. 



Habitat. Yucatan Strait, 640 fms., one valve. 



The comparison of this specimen with the fine series of this species in the 

 Jeffreys collection has confirmed the original identification. 



Genus ASTHENOTH^ERUS (Cpr. em.) Dall. 

 Asthenotharus Carpenter, Ann. Mag. Nat. Hist., XIII. p. 811, 1864. 



Shell inequivalve, inequilateral, truncate and slightly gaping behind, resem- 

 bling Periploma in shape ; beaks not fissured ; no external ligament ; hinge 

 linear, toothless and without fossette; a wide X-shaped ossicle attached to the 

 posterior slopes of the domes of the beaks above and behind the hinge-margin. 

 Pallial sinus deep ; gills like Periploma, siphons separated / foot small. Type 

 A. villosior Cpr., Cape St. Lucas. 



This group differs from Lyonsia in its Periploma-like shell, in having a trans- 

 Verse wide ossicle instead of a longitudinal narrow or triangular one; in being 

 anteriorly prolonged instead of posteriorly extended, and probably in the 

 character of the soft parts, which could not be well studied in the single dry 

 specimen available. It woiUd, indeed, seem to be a Periploma or Anatina, 

 destitute of the fossettes and their contained cartilage; in which the transverse 

 ossicle remains and the beaks are unfissured. The brown ligamentary basis on 

 which the divaricating feet of the bridge-like ossicle are planted, is visible on 

 each side through the shell, the brown lines simulating in position and appear- 

 ance, to a hasty glance, the fissures of Periploma. It is sufficiently separated 

 from Alicia by the edentulous hinge. 



The original and not very clear diagnosis of Dr. Carpenter does not mention 

 the ossicle, though the latter is still adhering (though not in its place) to one 

 of the valves of the type in the National Museum. The '" spongy ligament " 

 he refers to, is the brown cementum which originally held the ossiculum. 

 The original publication was to be followed by detailed notes, which remained 

 unpublished at the time of the author's death, which took place all too soon 

 for science. 



Asthenothserus Hemphillii, n. s. 



Shell small, yellowish white, concentrically striate, with a filmy epidermis, 

 left valve slightly smaller than the right, subovate, posteriorly truncated and 

 slightly gaping; beaks in the posterior third of the shell, the anterior part 

 rounded like the small cud of an egg-oval; base rounded, rising toward the 



