XOKTH A.MKKK'AN KAULY TERTIARY BRYOXOA. 91 



Variations. The aborted x.ooocia are closed with a median pore. The ances- 

 trula is elliptical and very small. The gymnocyst is more developed on the zooecia 

 close to the ancestrula : here. the frontal tuberosity is absent and the difference from 

 EUctra is indistinguishable. The characteristic interopesial cavities are developed 

 far from the ancestrula on the wider parts of the zoarinm. 



Affinities. This species differs from Conopc im hoocki'i'i- Ilaime. 18.">0, in its 

 much smaller frontal tuberosity and in its wider mural rim. 



It differs from ('<in<>/x'itni raiu'i* nun in its convex gymnocyst, and its mural 

 rim less enlarged at the base and not concave. 



Occurrence. Lower Jacksmiian (Moodys marl): :H miles north of Robert, 

 Newton County, Mississippi (rare). 



Holotype.CAt. No. c,:',si;s. V. S. X. M. 



CONOPEUM HOOCKEBI Haime, 1850. 



Plate 19. figs. 8-10. 



is.ji). Membranipont linockcri HAIME in D'Arohiac's Description Ues aiiiinaux fossiles clu 

 groups iiuininulitiqiif do I'luili-. Me iivs S.i.-i. - -i < leologique France, ser. 2, vol. 3, p. 227, pi. ::c,, 



fig. 5. 



isi HI. Minilii-iiniixini 7im7,vn Ki<:rss. I lie 1'nssileii Antlio/uen unil IJr.vnx.iieii I!IT Scliieliten- 

 gi-uiipi* vi >n C'rosarii. I>eiiksi-ln-it'l<Mi dcr k. Akailfinie tier YVissriisrliMt'ten, Wii-n. vol. 211. p. 411, pi. 

 3(i. fig. 14. 



l.sul. Membra ni pom lintirlcrri \V.vrn:.>-. Nm-th Italian Ur.vo7.ua. Quarterly Journal (Jcological 

 Siu-ii-'ty. I.onilon, vol. 47. p. 1",. 



Description. The zoarium incrusts shells. The zooecia have a marked luster 

 and are distinct, elongate, elliptical, somewhat narrowed posteriorly; the mural 

 rim is very thin, and sharply outlined, little enlarged at the base : the gymnocyst is 

 very convex. The opesium is regular in outline and elliptical. The interopesial 

 cavities are fusiform but rarely developed. The dorsal bears two distal impressions 

 which are excavated in the substratum. There is a distal septula and two septulae 

 are on each lateral wall. 



fAo = 0.30-0.31 mm. . [Z3= 0.36-0-38 mm. 



Meawrements.-Opesi* , 7 ,, =0 ls _ (V20 nim . IC13 \h=0.2 mm. 



A-ffinit'n-x. We have been unable to find Haime's original specimens in the 

 Museum of Natural History of Paris and verify the determination of Beuss. 

 There are some differences between onr specimens and Eeuss's figure which does 

 not indicate a hump-like, very constant gymnocyst. and iu which no interopesial 

 cavities are shown. Moreover. Waters indicates an opesium 0.35 mm. long, whercn- 

 onr own specimens measure only 0.31 mm. These are slight differences, and it 

 would be ridiculous to form a new species for four one-hundredths of a millimeter. 



On the other hand, the species is quite variable itself. The hump-like gymno- 

 cyst which is its fundamental characteristic, is often little developed and some- 

 times suppressed entirely: again, the zooecia are nut always M>paraied by a furrow 

 and the neighboring mural rims are closely adjacent. 



