EAELY TERTIARY CHEILOSTOME BRYOZOA. 15 



zooecia assume their normal size almost immediately. The absence 

 of gymnocyst and cryptocyst will distinguish this species easily 

 from Pyrvpora confluens Canu, 1907 (not Reuss). 



Occurrence. — Claibornian (Lisbon beds) ; Moseley's Ferry, Cald- 

 well County, Texas (rare). 



Type.—CBt. No. 62572, U.S.N.M. 



Genus HINCKSINA Norman, 1903. 



1903. Hhicksina Nobman, Natural History of East Finmark, Annals and 

 Magazine Natural History, (7) vol. 11, p. 585. 



Zocecia incrusting, having the entire area membraneous, the mar- 

 gin surmounted by numerous spines. Ovicell small, short, and lit- 

 tle raised. Avicularia occupying distinct cells sparingly scattered 

 among the zooecia, oval, with semicircular mandible. No dietellae. 

 (Norman.) 



Genotype. — Memhranlpora flustroides Hincks, 1880. 



Banff e. — Jacksonian-Recent. 



The American Early Tertiary species of Hincksina may be di- 

 vided into two sections, a new species of each of which is described 

 below. 



SECTION I. AVICULARIA LITTLE DIFFERENTIATED. 



HINCKSINA JACKSONICA, new species. 



Plate 1, fig. 6. 



Description. — The zoarium is free, bilamellar, easily divisible into 

 two layers. The zooecia are elongated, distinct, elliptical, often with 

 a small gymnocyst; the mural rim is convex, enlarged at the base, 

 finely granulated. The opesium is terminal, elliptical, regular, very 

 finely denticulated. The ovicell is endozocecial and little apparent; 

 it appears as a small distal convexity. Avicularian zocecia are very 

 rare. 



^. ^ . fho=0.35-0.45mm. 



Measurements.— Oi^esi^ lio=0.20-0.25 mm. 



Lz= 0.45-0.65 mm. 

 Zooecia lz= 0.35-0.40 mm. 



The two lamellae forming the zoarium separate very easily, each 

 preserving its own base. 



Variations. — The zooecial length is quite variable; both long and 

 short zocecia may occur. The avicularian zocecia or interzooecial 

 avicularia are rather rare. They are generally primoserial; their 

 opesium presents a lateral constriction but little accentuated. 



This species is distinguished from the other species of Hincksina 

 by the absence of visible spines and by its free zoarium. It is rather 

 common at many localities of the Jacksonian, of which it appears 

 to be a characteristic fossil. 



