358 bulletin: museum of comparative zoology. 



The specimens from the stations above, to wliich is prefixed an asterisk, — in 

 addition to being thinner-shelled, with a slightly more even curvature, circular aper- 

 ture, Avitli the longitudinal sculpture retaining its sliarpness to the end, instead of 

 flattening out as in typical megathyris, — have also at the anal end on the dorsal 

 side a notch which varies from 1.0 mm. to 7-0 mm. iu length, while in the 

 best preserved typical megathyris observed in the young stages, the anal aper- 

 ture is always entire. For this variety, which seems to grade into the type, the 

 varietal name oi panamense is proposed, though it may eventually prove to be a 

 distinct species. 



Dentalium peruvianum Dall, n. sp. 



Shell white, straight, except for a slight curve near the anal end which is at its 

 maximum about 20 mm. in front of the anal end; surface with an extremely thin, 

 yellowish periostracum, finely longitudinally striated, with wider slightly rounded 

 interspaces varying more or less in width ; these interspaces rise into thread-like 

 form near the anal end, where they alternate iu size, but are never very strong; 

 there are about twenty-six of them just in front of the slit ; in advance of this 

 point the intercalaries chiefly begin ; the anal end is rounded, about 1.75 mm. 

 in diameter, with a wide slit on the convexly arcuate or dorsal side, tlie slit at its 

 beginning is 17 mm. wide, and has a length of 5.0 mm. Tlie oral aperture is 

 nearly circular, measuring 12.0 mm. wide and 11.25 mm. dorso-ventrally ; the 

 margin is very sharp and thin ; the type specimen measures 90.0 mm. in lengtii, 

 of which two-thirds is nearly straight, the maximum deviation of the ventral sur- 

 face from a chord connecting the two extremities is 25 mm., about 20.0 mm. in 

 front of the anal end. 



U. S. S. " Albatross," station 4656, in 2222 fathoms, mud, off" the Peruvian 

 coast in S. Latitude 6° 55 'and W. Longitude S3° 34'; bottom temperature 35°. 2 F. 

 U. S. N. Mus. 110,607. Also at station 4649, in S. Latitude 5° 17' and W. Longi- 

 tude 85° 20', in 2235 fathoms, mud, temperature 35°.4, a fragment of the same 

 species. 



The type specimen had served as a pedestal for a large deep-water Actinia. 



The species is straightcr, more slender, and less tapering, and with a much 

 feebler sculpture than 1^. panamense, which is also shortf^r in proportion to its 

 oral diameter; D. ceras Watson, otherwise apparently its nearest relative, is quite 

 distinct, on comparison. 



Dentalium agassizii Ph.sbrt anp Sharp. 



Plate 4, flRiire K. 



Dentalium agosshii Pilsbry and Sharp, Man. Concli., 1897, 17, p. 20, pi. 12, figs. 

 90-94. 



The following table shows the various stations at which this species has been 

 dredged by the " Albatross " on her various cruises. 



