48 BULLETIN 96, UNITED STATES NATIONAL MUSEUM. 



The ovicelled zooecia, different in form from the others, have a 

 peristomice in the form of a lunar crescent without rimule-spiramen. 

 The frontal is a tremocyst with tubules. 



Genotype. — MetradoUum cUssimilis, new species. Jacksonian. 



METRADOLIUM DISSIMILIS, new species. 



Plate 4, tig. 10. 



Description. — The zoarium is free, bilamellar, branching; the 

 fronds are wide, thick, distorted or undulated, dichotomous. The 

 zocecia are distinct, elongated, elliptical. The frontal is a tremocyst 

 with tubules resting on an olocyst with very small pores correspond- 

 ing to the tubules. The peristomie is deep and very oblique ; the aper- 

 tura is small and suborbicular ; the peristomice is orbicular ; the spira- 

 men is median, more or less distant from the peristomice. There are 

 two oral avicularia symmetrically placed but dissimilar in form and 

 size ; the smaller is round, simple, nonsalient ; the larger is enormous, 

 oval, salient, with pivot. The ovicell is enormous, buried in the distal 

 zocecia, hyperstomial but opening largely into the peristomie ; salient 

 and globular; its peristomice has the form of a lunar crescent; the 

 ovicelled zooecia bear only a small avicularium with pivot. 



. \Jipe=0.U-0.1^ mm. 



Measurements.— PevistomicQ (exterior) W^^g—o i5_o.20 mm. 



|Z2=0.74-0.7G mm. 

 Zooecia (exterior) j^;,= 0.40-0.50 mm. 



Occurrence. — Middle Jacksonian: Wilmington, North Carolina 

 (very common), and various localities in South Carolina and Georgia. 

 Type.— OAi. No. 62596, U.S.N.M. 



LEIOSELLA, new genus. 



{Leios, smooth, having reference to the nature of the frontal.) 



The frontal is an olocyst. The peristomice of the ovicelled zooecia- 

 is of different form from that of the other zooecia ; it is a lunar cres- 

 cent and deprived of rimule-spiramen. 



Genotype. — Leiosella rostrifera.^ new species. Vicksburgian. 



This genus differs from Metradolium only in the nature of the 

 frontal, which is here a very thick olocyst. 



LEIOSELLA ROSTRIFERA, new species. 



Plate 5, fig. 1. 



Description.— T\\e zoarium is free, bilamellar; the fronds are nar- 

 row, flat, claviform, bifurcated. The zooecia are elongated, distinct, 

 ovoid ; the frontal is smooth, convex, formed by a thick olocyst. The 

 peristomice is irregular; the rimule-spiramen is bordered laterally 



