614 PALAEONTOLOGY OF ILLINOIS. 



Obverse face: Here the branches are strongly rounded, from 0.6 

 to 1 mm. wide, and appear to alternately approach and recede 

 from each other, so as to form elongate lozenge-shaped fenestrules. 

 Generally a narrow depression marks the line of junction between 

 the branches, causing the fenestrules to appear confluent. The fene- 

 strules are arranged in regular, diagonally intersecting and lon- 

 gitudinal series, with respectively 5.5 to 6 and 3.5 to 4 in the 

 length of 1 cm., each way. Zooecia usually in four ranges, with 

 three or five occasionally prevailing for a short distance. Aper- 

 tures sub-circular, small, with well developed but somewhat 

 oblique peristomes, arranged in more or less 1 regular transverse 

 rows, of which about seventeen occur in 5 mm. Transversely 

 the apertures are about their diameter apart, but longitudinally 

 the interspace is about twice as great. 



Reverse face: Here the branches are smooth, narrowly 

 rounded or angular, and with nearly flat sloping sides; the fene- 

 strules commonly rhomboidal, but sometimes regularly hexa- 

 gonal, and arranged in more or less curved intersecting series. 

 When of rhomboidal form there are exactly six in 1 cm., meas- 

 uring diagonally, and four in the same space vertically. 



This beautiful species is distinguished from all the Hamilton 

 Bryozoa known to me by its large fenestrules and the total 

 absence of non-poriferous dissepiments. Two or three smaller, 

 yet very similar species, occur in the Upper Helderberg and 

 Hamilton groups, but all of them have their zigzag branches 

 united by appreciable, though very short and wide, dissepiments. 



Position and locality: Hamilton group, Erie Co., N. Y. 



PINNATOPORA Vine, 1883.* 



(Fourth British Asso. Eept. on Foss Poly. p. 31.) 

 (For generic diagnosis see page 397.) 



This name justly supplants Glauconome in its common use 

 for Palaeozoic Bryozoa, the original species of that genus, being 

 of a very different type, and most probably congeneric with 

 those for which Defrance previously proposed the now well es- 



* The same name and for the same group of species was proposed by Mr. Shrub- 

 sole in 1884 (Proc. Chester Soc. Nat. Hist.) and conjointly by him and Mr. Vine in the 

 May number of the Quart. Jour. Geol'Soc., 1884. 



