754 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



their upper surfaces. From a primary branch short lateral branches 

 extend to the zoids, entering them at the distal end. The autozoids 

 (feeding individuals) are usually straight, or only slightly curved. In 

 length they range from 0.47 to 0.55 mm, and in w^idth they vary from 

 0.09 to 0.11 mm. Infrequently, an autozoid with a sharply pointed 

 rather than a bluntly rounded proximal end will be found. The ten- 

 tacles are 12 in number, determined from serial sections. The repro- 

 ductive zoid, the gonozoid, is usually as long as but may be slightly 

 shorter than the autozoid. Its proximal portion, extending below the 

 embryo chamber, is long, thin and slightly curved in the direction of the 

 embryo chamber. The embryo chamber is globular, giving the gonozoid 

 a "pot-bellied" appearance. The tentacle number of the gonozoid is 8, 

 but only in immature gonozoids will they be found, where the polypide 

 has not completely degenerated. 



The specimens described in the original report by Silen were collected 

 from South Africa and the Cape of Good Hope, and there was one 

 "doubtful" specimen from Panama. 



The specimens in the Hancock collection are from numerous localities 

 from San Pedro to La JoUa, southern California, all intertidal. 



Penetrantia concharum Silen, 1946 

 Plate 80, fig. 9 



Penetrantia concharum Silen, 1946:5. 

 Penetrantia concharum, Soule, 1950:360. 



The zoids of the colonies are well spaced, without the crowding noted 

 in P. densa. The openings in the shell are well defined, reniform in 

 shape. The autozoids are straight, slender, with the proximal extremity 

 tapering to a point. The autozoids range in length from 0.46 to 0.54 

 mm, and in width from 0.08 to 0.10 mm. The tentacles number 10, as 

 determined from sections. The gonozoids are comparatively rare. The 

 proximal extremity of the gonozoids is straight and visibly thicker than 

 the gonozoid of P. densa. 



Penetrantia concharum was found by Silen to occur in numerous 

 localities in Sweden and Norway. 



The specimens in the Hancock collection are from several localities 

 ranging from San Pedro to La Jolla in southern California and south- 

 ward to Rosarito, Lower California, Mexico (Hancock station 1597- 

 47). All are intertidal. 



