NORTH AMERICAN LATER TERTIARY AXD QUATERNARY BRYOZOA. 21 



tudinal rows in 3 mm. Opesium elongate nval. generally about twice as long as wide. Walls nearly 

 always a little less than half the -n-idth of the opesium. with a median channel, the ring-like elevation 

 enclosing the opesium uniformly elevated except across the anterior end where it is higher and obliquely 

 arched and elevated beneath, prolialdy to form a cover for an ooecium, and is usually surmounted bv 

 a transverse rib terminating at each end in a small roun<led prominence. Rarely the space of an ordinary 

 zooecium is taken up liy a cell havdng a thicker wall and a smaller aperture varying from elongate to 

 nearly circular, while iu one instance, a small cell with an oblique opening, narrowed distally, is 

 wedged in between three zooecia. 



,, . n, ■ [^0 = 0.36 mm. „ . fZ2 = 0.50 mm. 



Measurements. — Opesia , . „„ Zooecia , „ „„ 



^ (40 = 0.20 mm. ( /2 = 0.32 mm. 



Variations. — Our micrometric measurements represent the average; in reality 

 as in all the Membranipores the variations are considerable. The mural rim is 

 always somewhat wider in the proximal portion; the separating furrow is deep; 

 the opesium is finely crenulated. The two distal tubercles are placed generally 

 on the termen of the mural rim, but frequently they are attached to the exterior 

 slope and appear there as inserted in the interzooecial angles. We have not yet 

 discovered regenerated zooecia. 



We present a new photograph of the type of this species which brings out the 

 surface ornament and especially the tubercles more clearly. The species has 

 resemblance to both Conopeinn and Membranipora, but the apparent absence of 

 the two impressions on the dorsal wall of the zooecium, characteristic of Conopeum, 

 and the presence of the spines of Membranipora cause us to refer the species to 

 Membranipora in its restricted sense. 



Occurrence. — Miocene (Calvert formation): Reed's, Maryland (ver}- rare). 

 Miocene: Kuhns, Carteret County, North Carolina (rare). 



Plesiotyjn'.^Vsit. No. 68403, U.S.N.M. 



MEMBRANIPORA SPICUL.'ITA, new species. 



Plate 9, fig. 1. 



Description. — The zoarium encrusts species of Cellepora. The zooecia are 

 distinct, separated by a deep furrow, elliptical, elongated; the mural rim is thin, 

 salient, flat, bearing two distal tuberosities and two pairs of lateral spicules which 

 are conical and very salient. The opesium is of the same form as the zooecium. 



,, , r^ . [^0 = 0.32 mm. „ . fZ2 = 0.40nim. 



Measurements. — Opesia, „ ,„ Zooecia , _ „_ 



^ 1(0 = 0.18 mm. [ is = 0.30 mm. 



Affinities. — In its lateral spicules this species has much resemblance to Spiralaria 

 denticulata Busk, 1852, but it differs from it in the absence of an endozooecial ovicell 

 and in the presence of two lateral pairs of spicules. Hincl'sina serrata MacGillivray, 

 1881, also has a similar aspect, but in the present species we have not observed 

 either the oviceU or interzooecial avicularia. The spicules are rarely erect; they 

 are more or less curved in the form of a claw. The distal tuberosities are often 

 transformed into spicules. It is therefore rather probable that this species bears 

 an ovicell. But a single specimen has been found. 



Occurrence. — Miocene: Kuhns, Carteret Count}", North Carolina (rare). 



Holotype.— Cat. No. 68404, U.S.N.M. 



