46 BULLETIN 16 5, UNITED STATES NATIONAL MUSEUM 



simple Membranipore in which the spicules are joined along the 

 median axis above the ectocyst. 



The orifice of the zooecium is not a real aperture, since it is at 

 some distance and independent of the opercular valve. It is not, 

 moreover, an opesium, since the latter is located beneath the costules 

 and is not visible. In order not to add a new word to the nomen- 

 clature, we have simply called it the external aperture, since the 

 tentacles must necessarily pass through it. 



Lang, 1921, has explained very well the development of the median 

 process of the apertural bar. On certain species it fuses with the 

 proximal pair of apertural spines to form a shield above the proxi- 

 mal portion of the external aperture. In Lagynopora americana, 

 it is rarely developed and visible. 



We have not been able to determine the nature of the small inter- 

 zooecial heterozooecia ; they are very rare. 



Our micrometric measurements are those of the largest zooecia 

 observed on the two specimens in the National Museum collection. 



Affinities. — The three genera of Lang, 1916, Lagynopora, Hexa- 

 canthopora, and Prodromopora, differ from one another only in the 

 number of apertural spines and in the separation of the costules. 

 These characters, not corresponding to distinct variations of a 

 physiologic function, are not of generic value in our opinion, and 

 these genera should be united under the name of Lagynopora. No 

 species of this genus has been noted in the upper Danian either in 

 Europe or in America. 



Lang, 1921, has well described the calcified structure of the genus, 

 but he has not deduced the general structure without which a 

 natural classification is impossible. 



Occurrence. — Vincentown limesand : Very rare at Noxontown Mill- 

 pond, Del. 



Holotype.—U.S.'NM. No. 73900. 



Family ANDRIOPORIDAE Lang, 1916 

 Genus AEOLOPORA Lang, 1916 



AEOLOPORA GRANDIS, new species 



Plate 10, Figubes 1-3 



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

 tinct, separated by a deep furrow, elongated, elliptical, swollen, 

 relatively large; the frontal is very convex and formed by 8 or 9 

 pairs of regular costules not joined to one another and by an orbicu- 

 lar central area of fusion surrounded by a ring of beads; the aper- 

 tural bar is thick, convex, and forms an arch placed in front of the 

 orifice of the ovicell. The aperture is indistinct, transverse, oblique, 



