28 PROCEEDINGS OF THE NATIONAL MUSEUM vol.72 



Measurements. — Opesiumi n ~r. ^a ' 



fig = 0.48-0.50 mm. 



Structure. — The micrometric measurements shown on our speci- 

 mens differ very little from those which, we published in 1922. 



"The ovicell is transverse and formed by two calcified layers; the 

 superior one is very finely granulated, incomplete, surrounding an 

 area which is irregular and more or less linear. It is hyperstomial 

 and opens by a large special orifice which the opercular valve never 

 closes. The latter is bordered by a very thick sclerite. The mural 

 rim is granular and enlarged at the base." (Canu and Bassler, 

 1920.) 



"The granulation of the border varies with the amount of calcifi- 

 cation. Ooecia are present. In younger stages these are quite prom- 

 inent, but with latter calcification they become included in the general 

 crust." (Osburn, 1914.) 



Our specimens encrust shells, nuUipores, and debris. 

 Affinities. — This species is the equatorial representative of the 

 northern Alderina imbellis Hincks, 1860, but differs from it in its 

 transverse and nonelongated ovicell and its irregularly linear and 

 nonrectangular ovicellarian area. 



Under the name of Memhranipora irregularis the authors have 

 confused several species, and we gave the history of them in 1920. 

 The bibliography is only that which we indicate above because this 

 species was with certainty dredged only in the Gulf of Mexico. 

 Occurrence. — Albatross Station D. 2319, north of Cuba; 23° 10' 

 37" N.; 82° 20' 06" W.; 143 fms.; gray coral. 

 Albatross Station D. 2405, Gulf of Mexico; 28° 45' 

 00" N. ; 85° 02' 00" W. ; 30 fms. ; gray sand, broken 

 coral. 

 Albatross Station D. 2639, straits of Florida; 56 fms.; 

 coral sand. 



Pliocene : Minnitimmi Creek, Bocas Island, Almirante 

 Bay, Panama. 

 Plesiotypes.—C&t. Nos. 7451, 70831, U.S.N.M. 



ALDERINA (7) PYRIFORMIS, new species 



Plate 32, Figure .3 



Description. — The zoarium is unilamellar. The zooecia are dis- 

 tinct, separated by a deep furrow, elongated, pyriform, ornamented 

 sometimes with a short gymnocyst; the mural rim is salient, very 

 thin superiorly, enlarged at the base, with a sharp termen. There 

 are six distal spines placed on the exterior part of the mural rim and 

 often a pair of lateral spines. The ovicell is hyperstomial, salient, 



