BEYOZOA. 319 



Leptotrypa claviformls.] 



Leptotrtpa claviformis, n. sp. 



PLATE XXVII, FIGS. 20 and 21. 



Zoarium growing around and beyond one or more segments of Arthroclema and 

 Helopora into simple club-shaped forms varying from the smallest figured to one 

 that is 23 mm. long and 1.5 to 2.5 mm. in diameter. Some of the specimens have one 

 or two short lateral branches, in which cases the supporting body was a twig of 

 Arthroclema with lateral segments in place. Zooecial tubes growing about the axial 

 body very much as in ordinary ramose forms they grow about an imaginary center; 

 diaphragms abundant except in the outer or direct portion; walls thin. Zooecial 

 apertures subangular, nearly uniform in size, there being no appreciable clusters of 

 large cells; without apparent arrangement, about fourteen in 3 mm. What may be 

 mesopores, but more likely are merely young zooecia, are scattered among the 

 ordinary tubes. At intervals, however, they seem to be more numerous than usual. 

 Many, perhaps the majority, of the angles of junction are thickened and occupied by 

 projecting acanthopores. 



In a general way, this species may be said to fall under Leptotrypa, but I 

 am more than inclin^ed to doubt that it belongs there. The interior of the speci- 

 mens sectioned is but illy preserved, the finer details of structure being quite 

 obscure. Some of the specimens remind of Petigopora, Ulrich, and it is here that 

 better sections will probably cause us to refer them. 



Formation and locality.— 'Ra.ther common in the middle and upper thirds of the Trenton shales 

 at St. Paul and Minneapolis. 

 Mus. Beg. No. 8132. 



Family CERAMOPORID^, Ulrich. 

 Genus SPATIOPORA, Ulrich. 



Spatiopora, Ur.KiCH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 155, and 1883, vol. vi, p. 166; Fooed, 



1883, Contri. Micro-Pal. Camhro-Sil. Books, Can., p. 20: Ulkich, 

 I 1890, Geol. Surv. 111., vol. viii, p. 381. 



Zoaria forming thin parasitic crusts upon foreign bodies, the shells of Orthoceras 

 being the most favored. Surface even or with monticules. Zooecia short, with 

 direct and more or less irregularly shaped apertures. Lunarium scarcely perceptible 

 even in thin sections. Mesopores very few, usually absent, when present occurring 

 chiefly as "maculae." Interspaces often with large blunt spines (? acanthopores). 

 Walls of zooecia moderately thin, with the characteristic structure pertaining to the 



family. 



Type : S. asp$ra Ulrich. 



