THE NAUTILUS. 123 



ing obliquely forward, and with their connecting resilium sustaining 

 a proportionately large triangular lithodesma ; the chondrophores 

 are supported behind by well-developed clavicular props, which are 

 inserted posteriorly on the surface of the valve below the linear 

 hingeline. Length 32, height 27, diameter of right valve 6 and of 

 the left valve 4 mm. 



This elegant shell, in a somewhat damaged condition, was thrown 

 upon the beach at San Pedro, Cal., after one of the heavy winter 

 storms and collected by Mrs. T. S. Oldroyd, to whom we owe so 

 many additions to the fauna of this region. 



This species is, we believe, the first Periploma known to possess an 

 undulated sculpture, and bears to those of the ordinary type such a 

 relation as that of Cyathodonta to Thracia or Lnbiosa to Raeta. The 

 differences of sculpture and in the form of the lithodesma suggest 

 that, as in the case above cited, P. sulcata is entitled to a sectional 

 name for which Halisirepta is proposed. 



A NEW DENTALIITM FROM CALIFORNIA. 



BT WILLIA:\r J. RAYMOND. 



Dentalhtm vallicolens n. sp. 



Adult shell large, rather slender, moderately curved posteriorly, 

 the latter half nearly straight; cream-white, often yellowish toward 

 the mouth, shining where not eroded, earlier portion usually dull ;ind 

 chalky because of erosion ; growth-lines fine, irregular, distinct, 

 rarely an encircling groove due to repaired fractui'e ; at the apex 

 there are longitudinal, low, rounded, inconspicuous threads, of which 

 seven or eight are more prominent and three to six in each inter- 

 space are less prominent ; these die out, and fine, superficial striae 

 appear, visible under the glass and continued to the mouth of the 

 shell, seven or eight per millimeter of circumference ; aperture 

 simple, circular, mouth slightly oblique. 



Two specimens measure : length 64.5, diam. of aperture ;>.3, of 

 apex 1.5, at middle '4.6, height of arch from chord 2.5 mm.; length 

 64.0, diam. of ai)erture 4.7, of apex 1.4, at middle 4.2, height of 

 arch from chord 3.0 mm. 



Young shell strongly curved, very slender for the first eight or 

 ten millimeters of length, then rapidly enlarging; at first seven or 



