416 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



secondary layer is laid down by growth from the areolar pores toward 

 the center in the fashion of a pleurocyst. The peristome is thin and 

 usually low, but sometimes rises to a considerable height on the sides 

 and may surround the proximal border of the aperture. The primary 

 aperture is nearly round, only slightly wider than long (0.15 mm wide) ; 

 the lyrula moderately developed, not more than one-third the width of 

 the aperture, transverse at the tip and the corners not extended. 



Small, pointed, oval or short-spatulate avicularia are variously dis- 

 tributed on the front and usually directed laterally; at the side of the 

 peristome there is frequently a giant avicularium with a long sub- 

 spatulate mandible (the sides gradually narrowing toward the tip) 

 directed forward and often somewhat curved around the peristome, the 

 mandible as long as 0.40 mm but usually shorter. The oral spines number 

 one to three, small and very evanescent. 



The ovicell is large, about 0.35 mm in width, roughened and heavily 

 calcified like the frontal, with a few large pores and with the peristome 

 extended across the front. 



This is evidently the species which Dr. Robertson described as a 

 Mucronella, but the supposed mucro is undoubtedly a lyrula and the 

 peristome extends behind it; the presence of avicularia similar to those 

 common in Parasmittina and the nature of the ovicell also relate it to 

 the latter genus. Robertson recorded it from "several localities on the 

 coast of southern California," and "dredged off the island of Santa 

 Catalina." 



As in many other species there is a distinct bathymetric change to 

 the southward ; all of the southern California localities are less than 50 

 fms, those in Mexican waters are around 50 to 60, and the one Galapagos 

 station was 100 to 150 fms. 



Hancock Stations: 1281-41, Santa Rosa Island; 1327-41, San Cle- 

 mente Island; off Santa Catalina Island, off La Jolla and several other 

 localities without specific data, southern California. Stations 1008-39 

 and 1250-41, San Benito Islands, and 1264-41, Cedros Island, off Lower 

 California; 557-36, Isla Partida, Gulf of California, and 143-34, Wen- 

 man Island, Galapagos. 



Parasmittina collifera (Robertson), 1908 

 Plate 49, figs. 9-11 



Smittia collifera Robertson, 1908 :304. 

 Smittia collifera, O'Donoghue, 1923 :43. 

 Smittina collifera, O'Donoghue, 1926 :68. 



