72 BULLETIN 16 5, UNITED STATES NATIONAL MUSEUM 



doubtful. Our specimens are poorly preserved and too rare to make 

 a detailed study of the species. 



Occu?Tence. — Vincentown limesand : Very rare at Noxontown Mill- 

 pond, Del. 



Holotype.— U.S.N. M. No. 73890. 



DIPLOTRESIS," new genus 



Hippothoidae in which the zooecial frontal bears two frontal pores 

 (ascopores?). There are zooeciules with pointed beak, irregularly 

 arranged between the zooecia. The ovicell is hyperstomial and closed 

 by the operculum. 



Genotype. — Diplotresis {Microporella) sparsiporosa Ulrich and 

 Bassler, 1907. 



In the Cyclostomata, the studies of the minute cells, nanozoids, 

 was made by Borg, 1926. In the Cheilostomata, the study of the 

 similar zooeciules has not yet been undertaken. Their anatomy and 

 their function are unknown, so that it is difficult to determine the 

 importance that should be given them in the classification. 



Zooeciules analogous to those of the genus Diplotresis have been 

 discovered in the membranimorph genus Marssonopora Lang, 1912, 

 and in the Cribrimorphs Otopora Lang, 1916, and Barroisina Jullien, 

 1886. 



DIPLOTRESIS SPARSIPOROSA Ulrich and Bassler, 1907 



Plate 17, Figures 6, 7 



1907. Microporella sparsiporosa Ulbioh and Bassler, in Weller, Geol. Surv. 

 New Jersey, Paleontology, vol. 4, p. 348, pi. 26, fig. S. 



Description. — The zoarium encrusts small stones and the frag- 

 ments of shells. The zooecia are distinct, separated by a deep fur- 

 row, much elongated, oval or fusiform; the frontal is quite convex 

 and perforated by a large number of small pores regularly arranged 

 in transverse rows. The ascopore, little removed from the aperture, 

 is formed of two small pores arranged symmetrically on each side of 

 a small median tuberosity. The aperture is terminal, semielliptical, 

 transverse ; the peristome is complete, thin, very salient, surrounding 

 a short peristomie. The ovicell is hyperstomial, resting on the distal 

 zooecium, closed by the operculum, globular, large, finely punctate. 

 The zooeciules are long narrow, fusiform, irregularly arranged be- 

 tween the zooecia, isolated, rarely grouped; the frontal is finely 

 porous; the beak is quite long, acuminate, and terminated by a 

 canalicule. 



Measurements. — 



rj . [Lz= 0.65-0.7 mm. . \ha=0M mm. 



Zooecia aoka^ Apertura 



uz= 0.35-0.4 mm. [?a=0.1 mm. 



H From SnrXSos, double + rpijcm, perforation; referring to the two frontal pores. 



