34 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



often move in unison and when stimulated they may stand erect for some 

 time. The vibracular chamber is prominent and its aperture is lunate, 

 with one side higher than the other. The vibracula and the frontal 

 membrane, especially near the walls, are brownish in color. The dorsal 

 side shows small quadrangular areas with usually four pores in each area. 



While the form of the colony and the arrangement of the zooecia are 

 usually quite regular, exceptions are not uncommon. The larvae usually 

 attach themselves to small objects, especially sand grains, and grow free 

 and symmetrically beyond the edges, but occasionally they attach on 

 larger irregular objects and become distorted. The C. elongata of Saka- 

 kura (1935:6) is an example of the same sort of irregularity in C. 

 guineensis (Busk). The writer has a specimen of canariensis which be- 

 came attached to the inside of a shell where it followed the curvature 

 of the shell, becoming concave on the frontal surface. 



This species appears to be limited to the Atlantic and the Mediter- 

 ranean Sea and the Pacific coast of North America. It is an abundant 

 form in the Gulf of Mexico, but it has hitherto escaped notice on the 

 Pacific coast except for Hastings' record at Gorgona, Colombia. Robert- 

 son's record (1908:314) is due to a misidentification, as she undoubtedly 

 had Discoporella unbellata (Def ranee). 



The range of the species on the Pacific coast, as determined by the 

 Hancock dredgings, is from Cedros (Cerros) Island, half way down the 

 coast of Lower California, to Ecuador and the Galapagos Islands. Inter- 

 mediate stations, more than 30, include the Gulf of California, Clarion 

 and Socorro Islands west of Mexico, the west coast of Mexico, Costa 

 Rica, Panama, and Colombia. It occurs in shallow water and down to 

 40 fathoms, but appears to be more abundant from 10 to 20 fathoms. 



Family Electrinidae d'Orbigny, 1851 



The zoarium is usually encrusting, but may be erected from an en- 

 crusting base. The zooecia are usually provided with a well-developed 

 gymnocyst but this is sometimes vestigial and both extremes may some- 

 times be seen on the same colony. There are no ovicells, no avicularia, 

 and no dietellae. Spines are usually present around the border of the 

 opesia, occasionally wanting, in some cases limited to a single strong 

 median proximal spine which may be reduced to a mere tubercle or be very 

 greatly elongated. The simple nature of the zooecia, except for the spines, 

 relates this group to the more primitive membranipores. 



