110 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



tions 2824 and 2825, all in the southern part of the Gulf of California; 

 132-34, Socorro Island and 136-34, Clarion Island, west of Mexico; and 

 212-34, La Plata Island, Ecuador. Also Gulf of Panama, Galtsoff collec- 

 tion on pearl oysters. The known range on the Pacific coast is from 25° 

 57'00"N, in the Gulf of California, to 1°15'00''S, Ecuador; shore down 

 to 47 fms. 



Family Thalamoporellidac Levinsen, 1909 



Levinsen, 1909:175-178, gives an extended discussion which it is not 

 necessary to repeat here. The opesiules are closed, often unsymmetrical 

 in size and form and often extend to the dorsal wall ; the cryptocyst ex- 

 tends far forward leaving a rounded opesia, most of which is occupied 

 by the operculum. At the side of the operculum are adoral areas, often 

 vestigial, which may bear tubercles. In the body cavity occur peculiar 

 spicules shaped like wide-open compasses and curved calipers. The avicu- 

 laria are large, replacing zooecia in the series. Ooecia very large and 

 prominent, somewhat bilobate, and closed by a special membrane. 



Genus THALAMOPORELLA Hincks, 1887 

 Characters of the family. Genotype. F lustra rozieri Audouin, 1826. 



Thalamoporella gothica (Busk), 1856 

 Plate 12, fig. 1 

 Membranipor a gothica Busk, 1856:176. 



Thalamoporella rozieri yzr.Y) {gothica) Levinsen, 1909:184. 

 Thalamoporella gothica^ Harmer, 1926:302. 



Zoarium encrusting or erect. Zooecia large (0.80 to 1.10 mm long 

 by 0.30 to 0.50 mm wide), the sides usually parallel. The cryptocyst 

 covers two-thirds or more of the front, thickly perforated to the level of 

 the opesiules. The opesiules are large, often differing in size, the wall 

 of one usually descending to the dorsal side. The opesia is distinctly 

 sinuate on the proximal border, 0.30 to 0.35 mm in each dimension, occa- 

 sionally with adoral tubercles on the side, but usually the aperture oc- 

 cupies the full width within the mural rim and leaves no adoral areas. 

 The operculum is thin with a well chitinized rim and the sclerite of the 

 proximal border is complete but narrow. 



The avicularia are large, the chamber about as long as the Zooecia 

 but narrower; the mandible varies, 0.40 to 0.55 mm long by about 0.25 

 mm wide at the base ; the main sclerites are straight and extend forward 

 to their junction near the curved tip ; the condyles are strong and partially 



