156 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



CALLOPORA MUNDULA, new species. 



Plate 29, fig. 12. 



Description. The zoarium is bilamcllar, free, composed of large, flat, fronds; 

 the two lamellae are back to back and inseparable. The zooecia are large, elongated, 

 distinct, separated by a deep furrow; the mural rim is thin distally, enlarged 

 proximally, rounded or angular. The opesium is regular, elliptical, elongated. 

 The ovicell is globular, salient, smooth ; it is hyperstomial and opened in a special 

 orifice above the operculum. The avicularium is frontal, large, elliptical with two 

 lateral denticles. 



. [Ao=0.55 mm. . fZs=0.75-1.00 mm. 



Measurements. Opesia , nc .. Zooecia 7 r 



|?o=0.28 mm. [3=0.35-0.40 mm. 



Affinities. This neat and elegant species appears to be the largest species of 

 Callopora. In general aspect it approaches Grammella transversa; it differs from it 

 in the longitudinal and non-transverse orientation of its avicularium and its bifoli- 

 ate and not incrusting zoarium. 



Occurrence. Lower Jacksonian (Moodys marl): Jackson, Mississippi (rare). 



Holotype.Czt. No. 63928, U.S.N.M. 



Genus AMPHIBLESTRUM Gray, 1848. 







1848. Arnphiblcstntm GEAT, List British Animals British Museum, Centroniae, pp. 110, 146. 

 1903. Amphiblestrum. NOKMAN, Notes Natural History East Pinmark, Annals and Magazine 

 Natural History, ser. 7, vol. 11. p. 596. 



Hinder portion of the area covered with a calcareous crust. In front of this a 

 considerable portion of the area, typically trifoliate, but sometimes semielliptical 

 or subrotund, is covered only by a thin membrane, at the distal extremity of which 

 is situated the simple oral opening. Margin of zooecium thickened, often granu- 

 lated, sometimes bearing a pair (or more) of lateral spines found in young speci- 

 mens. Reproduction by means of prominent hyperstomial ovicells never closed by 

 the operculum. Sessile avicularia often present, sometimes one, sometimes two, 

 on the hinder portion of the zooecium. Dietellae, two pairs of lateral and one distal. 

 (After Norman.) 



Genotype. Amphiblestrum (M enibranipora) ficmingii Busk. 1852. 



Range. Senonian-Recent. 



This is in part the Membranipora femingii group of Waters which he defined as 

 follows: "Ovicells with more or less arched area on the front; usually lamina over 

 considerable part of the front. Pore chambers.'' 



The opesium often appears trifoliate. The distal part is occupied by the oper- 

 cular valve for which the opesial contraction serves as a pivot. The proximal por- 

 tion, which is the larger, is occupied by the chitinous part of the cryptocyst on which 

 the parietal muscles are inserted. The calcareous cryptocyst, the chitinous crvpto- 

 cyst, and the opercular valve form a structure in direct contact with the ectocyst.. 

 The entire structure is covered by a thin ectocyst united at the opercular valve 

 which is thus thickened and often bordered with a sclerite. Between the chitinous 



