BRYOZOA. 317 



Leptotrypa hexagonalls.l 



from the types of growth mentioned in the description. Numerous species of both 

 genera are known and several of Leptotrypa from the Trenton beds of Minnesota, 

 True Amplexopora, however, is first met with in the Utica.* 



Leptotrypa hexagonalis Ulrich. 



(Not Figured.) 

 Leptotrypa hexagonalis, Ulkich, 1890. Geol. Surv. 111., vol. viii, p. 455. 



Original description: "Zoarium forming parasitic expansions less than 1 mm. 

 in thickness, spread upon Orthoceras and Hyollthes. Surface smooth. Clusters of 

 cell apertures of almost twice the usual size are arranged in diagonally intersecting 

 rows; these clusters are about 3 mm. apart, measuring from center to center. Zocecia 

 regularly hexagonal in shape, sometimes a little elongated, seven, measuring longi- 

 tudinally, almost nine, diagonally, in 2 mm.; diameter of the smaller 0.2, of the 

 larger 0.35 mm. Acanthopores prominent on the surface when well preserved," 



This species occurs almost invariably as a delicate lace-like expansion upon 

 Hyolithes baconi Whitfield. This fact, together with the markedly hexagonal shape 

 of the zooecial apertures, renders it an easily recognized species. 



Formation and locality.— Ra.theT rare in thejlmestone at Minneapolis, Minnesota. The types are 

 from equivalent beds ("Lower Blue") at Mineral Point, Wisconsin, and Calhoun county, Illinois. Other 

 localities are Janesville and Beloit, Wisconsin. 



Mus. Beg. Nos. 7551, 7557, 7595. 



Leptotrypa informis, n. sp. 



PLATE XXVIl, FIGS. 22 and 23. 



Zoarium forming parasitic patches or lump-like growths upon foreign bodies, 

 varying considerably in size and from 1 to 5 mm. in thickness. At other times 

 apparently free, with a wrinkled epitheca beneath. Surface without monticules, 

 nor are the clusters of large cells very conspicuous except in a few cases where the 

 zooecia forming them 9,re separated by a limited number of small cells. Zooecial 

 apertures polygonal, thirteen or fourteen of the average size in 3 mm. Walls very 

 thin, in vertical sections sometimes appearing as though made up of alternating 

 horizontal bands of light and dark shades. Acanthopores more or less prominent 

 at the surface, varying some in size, restricted to the angles of junction, one-half of 

 which are occupied by them. Diaphragms complete, on the whole rather remote 

 and irregularly distributed, the intervals between them varying from one to four 

 times their diameter. 



^^Treiiton suedes have been placed under Amplexopora by both Mr. A. H. Foord and myself, but a re-examinatlon 



has convinced me that the species In question are more likely aberrant types of Batostoma, where I would bow place 

 them. 



