NO. 3 OSBURN : EASTERN PACIFIC BRYOZOA CYCLOSTOMATA 755 



Penetrantia sileni Soule, 1950 



Plate 80, fig. 10 



Penetrantia sileni Soule, 1950:361. 



The openings in the scaphopod shell made by this species vary con- 

 siderably in shape, from a simple circular to a highly exaggerated reni- 

 form appearance. The stolon is thin, not serrated on its upper surface, 

 and is in general circular in cross section. The zoids are placed close to 

 each other but are not crowded. The autozoid ranges in length from 

 0.35 to 0.36 mm, and in width from 0.07 to 0.08 mm. The autozoids 

 may be slightly curved, and they may have a pointed rather than a 

 rounded proximal extremity. The tentacle number, as determined from 

 serial sections, is 11. The mature gonozoid has a very characteristic 

 morphology. It is little more than one-half the length of the autozoid, 

 ranging from 0.19 to 0.20 mm in length. The narrowed proximal portion 

 barely reaches below the swollen embryo chamber. 



Specimens in the Hancock collection are from off the San Benito 

 Islands, Mexico, Hancock station 1010-39, 28°12'05"N, 115°33'45"W. 

 The depth range is from 71 to 86 fathoms. It is as yet known only 

 from the eastern Pacific. 



