36 PROCEEDINGS OF THE NATIONAL MUSEUM vol, 72 



Structure. — The frontal is formed by more or less coalesced spines; 

 it is not covered by an ectocyst. The real frontal ectocyst is arranged 

 under the ensemble of costules; it bears the true aperture closed by 

 a simple valve. 



Smitt, 1864, noted the flustrine nature of the genotype Lepralia 

 nitida Johnston, 1848 (that is to say, the absence of a compensatrix) , 

 and figured (pi. 6, fig. 1) the parietal muscular system. Also in 

 1867 he placed it in Membranipora. Levinsen, 1909, established the 

 great analogy of the genus Membraniporella with Callopora Gray, 

 1848. Finally, in the paleontologic evolution, the cribrimorphs began 

 with Membranipora and have always accompanied them since the 

 Cenomanian. There is then no longer any serious reason for putting 

 the two groups in distinct families. The union of the spines above 

 the ectocyst is only a manifestation of calcification and solely a par- 

 ticular means of adaptation or of protection. Is this union of the 

 spines such an essential function of the animal as to justify the crea- 

 tion of a special genus? We still do not know. However, as this 

 generic distinction appears to facilitate the determination, we main- 

 tain it and recognize the genus Memhraniporella, classing it in the 

 Calloporidae. For the same reason we ought to create a cribrimorph 

 genus corresponding to each of the membraniporoid genera provided 

 with areal spines. We have some examples in the Hincksina stage. 

 In the Membranipores the aperture is always bordered by a sclerite 

 formed by the chitinous thickening of the ectocyst; the opercular valve 

 closes exactly with the peripheral sclerite. In drawings of the oper- 

 cular valve they are always separated in order to show their presence. 

 The apertural sclerite no longer exits in the cribrimorphs, for it has 

 become useless, the ectocyst adhering to the calcareous armature 

 which surrounds the aperture. Our drawings of the valves of the 

 cribrimorphs can then indicate only the single opercular sclerite. 



The visible exterior orifice is not the true aperture since the latter 

 opens on the subadjacent ectocyst, but as it has exactly the same 

 form it is the custom to name it also aperture. 



MEMBRANIPORELLA PETASUS, new species 



Plate 4, Figures 1, 2 



Description. — The zoarium encrusts nuUipores and chitinous 

 sponges. The zooecia are distinct, separated by a deep furrow, 

 elliptical, elongated, swollen; the frontal is quite convex; the costules 

 are broad, flat, 9-10 in number, separated by linear lacunae in the mid- 

 dle of their length and by small irregular lacunae in the vicinity of 

 the median axis. The opesium is semielUptical, transverse, with a 

 concave proximal border, larger and with the form of a hat on the 

 ovicelled zooecia; the peristome bears three or four short palmate 

 bifid spines, of which the two lateral ones are wide and in the 



