BRYOZOA. 501 



mm. Margin sharp, with a wide non-poriferous border. Sur- 

 face smooth, with inconspicuous solid maculae on a level with 

 or slightly depressed below the general surface, at variable dis- 

 tances apart. Apertures sub-pjriform to sub-circular, 0.12 to 

 0.15 mm. in diameter, with uneqally elevated peristome, about 

 one and one-half or two times their diameter apart, arranged 

 in diagonally intersecting series, seven or eight in three mm. 

 Internal structure like that of the preceding species, but the 

 vesicles are very crowded vertically and smaller in tangential 

 sections. The solid tissue near the surface is lined longitudin- 

 ally rather than concentrically. Lunaria pronounced, constitut- 

 ing a conspicuous feature in tangential sections. 



This species in its subramose zoarium and better developed 

 hmariuni approaches Cystodictya. The propriety of referring 

 the species to Diehotrypa rather than to Cystodictya, scarcely 

 admits of question. 



Position and locality: St. Louis group; Alton, 111.; St. Louis, 

 Mo. 



DlCHOTRYPA EXPATIATA. 

 Not figured. 



So far as observed, this species closely resembles D. intermedia 

 in nearly all its minute characters, but differs so strikingly in 

 the form of the zoarium, that I am inclined to believe that bet- 

 ter material than is now at hand, will show corresponding zooe- 

 cial differences. The zoaria before me have grown into large 

 thin undulating expansions, one of them (incomplete) being 

 about 15.5 cm. long by 11 cm. wide: its thickness varies from 

 0.7 to 2.0 mm. 



Whether specifically distinct from D. intermedia or not, the 

 two forms are easily distinguished, and I have, therefore, 

 thought it desirable that they be known by separate names. 



Position and locality: St. Louis group; Alton, 111. 



DICHOTRYPA FLABELLUM Romiuger. 



PI. LXXVII, fig. 1-lb. 

 Upora flalteUnm Rominger, 1866. Proc. Acad. Nat. Sci.Phila. p. 122. 



Zoarium having a strong, expanded base, roughly marked on 

 the lower side with a concentrically wrinkled epitheca. On the 



