90 THE PALEONTOLOGY OF MINNESOTA. 



LStreptelasnm. 



is .so remote that I cannot hesitate to describe it as new, and as a matured form. 

 Against these being young corallites I would urge (1) their nearly equal size, and (2) 

 their crowded habit of growth. They could not have grown to larger size except by 

 becoming detached from the supporting body, which is a supposition so unlikely that 

 it is not to be entertained for a moment. 



Where the calices are in contact the appearance is decidedly suggestive of 

 Columnaria, and, while I doubt it, this resemblance may really indicate true relation- 

 ship. For the present it seems to me the species may well be arranged as above 

 under Streptelasma near S. profundum. There it can remain till we learn more of its 

 characters, or until the genus Streptelasma is redefined and strictly characterized. 

 And right here I wish to say that no genus of paleozoic corals is less understood and 

 more in need of revision than Streptelasma. As now used it is made to include some 

 very diverse. types. 



Formation and locality. Bare in the middle division of the Trenton shales at St. Paul, Minnesota. 

 Another specimen, consisting of six corallites, of the same or a closely related species, was collected by 

 me from the Trenton limestone at Minneapolis. Now in my collection. 



STREPTELASMA CORNICULUM Hall. 



PLATE G, FIGS. 20, 21. 



1847. Streptoplasma corniculum HALL. Palaeontology of New York, vol. i, p. 69. 



1847. Streptelasma corniculum HALL. Ibidem, pi. 25, figs, la-le. 



1847. Streptoplasma crassa HALL. Ibidem, p. 70. 



1847. Streptelasma crassa HALL. Ibidem, pi. 25, flgs. 2a-2c. 



1847. Streptoplasma multilamellosa HALL. Ibidem, p. 70. 



1847. Streptelasma multilamellosa HALL. Ibidem, pi. 25, flgs. 3a-3c. 



1847. Streptoplasma parvula HALL. Ibidem, p. 71. 



1847. Streptelasma parvula HALL. Ibidem, pi. 25, flgs. 4a-4c. 



1857. Streptelasma corniculum BILLINGS. Canadian Naturalist and Geologist, vol. i, p. 122, flgs. 3 



and 4, on p. 121. 



1863. Petraia corniculum BILLINGS. Geology of Canada, p. 156, fig. 118, and p. 938. 



1875. Streptelasma corniculum NICHOLSON. Paleontology of Ontario, p. 12, (p. 26 partim). 



Original description. " Turbinate, curved near the base, which terminates in an 

 acute point, somewhat rapidly expanding above ; cup profound ; lamellae about 

 sixty ; surface marked by strong longitudinal lines indicating the lamellae, which are 

 crossed by fine concentric wrinkled lines. 



"Length varying from three-fourths to one and a half inches." 

 Corallum conical, more or less curved, greatest length observed 45 mm., with a 

 diameter of 27 mm.; slightly attached. Exterior exhibiting longitudinal lines cor- 

 responding with the larger septa within, those on the dorsal side converging to the* 

 cardinal and alar septa ; rarely smooth and commonly with folds of growth. Calyx 

 more or less deep with three fossulae, the cardinal one most prominent placed on the 

 dorsal or convex side of the corallum, with the others disposed laterally. Septa 



