NORTH AMERICAN EARLY TERTIARY BRYOZOA. 585 



limited this genus to only those species whose ovicell is provided with a cribriform 

 area. We are ignorant of the physiologic significance of this area, and we are 

 nimble to discuss the subject from a study of more or less well-preserved fossil forms. 



This species differs from Perigastrella tulmlosa, which is also provided with 

 a long peristomie, in its iuterareolar costules. and in its smaller micrometric dimen- 

 sions (Z2=0.45 and not 0.65 mm.). 



Perig'astreUa grotiani Reuss, 1865, is also provided with an exterior tubular 

 peristomie, but our species differs in its more scattered areolae and in the presence 

 of interareolar costules. 



It is to be noted that this species does not spread out into flabelliform zoaria. 

 We- have observed it only on very narrow substrata, such as would be offered by 

 the cyclostome bryozoa. It is not possible to comprehend how a wide substratum 

 is capable of destroying larvae; we must therefore admit that a larva is capable 

 of choosing its substratum, which is marvelous in the obscure depths of the sea. 

 Such symbiosis is frequent everywhere in the bryozoa. 



Occurrence. Vicksburgian (Marianna limestone) : West bank of Conecuh 

 River, Escambia County, Alabama (common) ; Murder Creek, east of Castlebury, 

 Alabama (very rare). 



Cotypes.G&i. No. 64323, U.S.N.M. 



PERIGASTRELLA? TUBULOSA, new species. 

 Plate 74, fig. 1. 



Description. The zoarium incrusts shells. The zooecia are distinct, long, 

 lageniform; the frontal is very convex, smooth, surrounded by very fine areolae. 

 The apertura is deep, suborbicular, and formed of a large semilunar anter separated 

 by two small cardelles from a very concave poster; the peristome bears six distal 

 spines. The ovicell is smooth, globular, salient; it, is hyperstomial. recumbent, 

 opening largely in the peristomie; it is surrounded by a very little salient collar. 



,. .. . . 



Measurements. Apertura , /ooeciai, n 



\la 0.13mm. ife=0.30mm. 



Affinities. This species presents all the characters which would permit its 

 classification in Lagcnipora Hincks, 1888. However, its ovicell is not placed as 

 in Lagenipora socinlis Hincks, 1877, and does not bear the cribriform area noted 

 by Waters. On the other hand, the apertura with cardelles is a little different 

 from the semielliptical apertura of the other species of Perigastrella. Finally the 

 peristomiale is not free, which was u fundamental character according to Hincks. 

 The generic place of this species is therefore doubtful. 



It differs from Perigastrella.'* cost if era of the same lageniform group in its 

 zooecial size (Ls=O.Go and not 0.45 mm.) and in its smooth frontal. 



Occurrence. Upper Jacksonian (Ocala limestone) : Chipola River, east of 

 Marianna, Jackson County, Florida (common). 



Holotypc.C&t. No. 64204, U.S.N.M. 



