80 THE PALEONTOLOGY OF MINNESOTA. 



ISolenopora. 



"The radiating canals are a little smaller than in the common H. spheroidalis 

 Duncan, of the Niagara, being as a rule not over 0.27 mm. in diameter. H. incequalis 

 Ulrich, from the lower or sponge beds of the Trenton limestone at Dixon, Illinois, is 

 larger and has, as its name may indicate, radiating canals of very unequal size." 



The specimens of this species occurring in the Galena of Kentucky, Tennessee, 

 \\ i.sconsin, and Minnesota, the localities from which Mr. Ulrich obtained his mate- 

 rial, should not at present be regarded as belonging to Microspongiu gregaria Miller 

 and Dyer. The latter is not shown to be identical with Hindia, and, as the Galena 

 specimens undoubtedly belong to the last named genus, there is no evidence that 

 H. parva is synonymous with Microspongia gregaria. The varieties of Hindia parva 

 found at Cincinnati and Middletown, Ohio, of which Mr. Ulrich writes op. cit., p. 

 243), may be the same as Miller and Dyer's species, but this the writers cannot prove, 

 as they have no material from Ohio for comparison. 



Formation and locality. Hare in the Trenton shales at Minneapolis, Minnesota. Not uncommon in 

 the Galena of Goodhue county, Minnesota, and Oshkosh, Wisconsin. Also from a similar horizon at Dan- 

 ville and Frankfort, Kentucky, and south of Nashville, Tennessee. 



Colkctors W. H. Scofleld, E. O. Ulrich and C. Schuchert. 

 Mus. Beg. No. 7711. 



? Class HYDROZOA. 

 ?Sub-Class HYDRO1DA. 



SOLENOPORA, Dybowski. 

 SOLENOPORA COMPACTA Billings. 



PLATE F, FIGS. 21-23. 



1862. Stromatopora compacta BILLINGS. Palaeozoic Fossils, vol. i, pp. 55, 210. 

 ?1877. Tetradium peachii NICHOLSON and ETHEKIDGE. Annals and Magazine of Natural History, 



ser. iv, vol. xx, p. 166. 

 V 1877. Solenopora spongioides DYBOWSKI. Die Cbastetiden der ostbaltischen Silur Formation, 



p. 124, pi. 2. 



1879. Solenopora("i) compacta DAWSON. Quart. Jour. Geological Society, London, vol. xxxv, p. 53. 

 1883. Tetradium peachii, var. canadense FOOED. Contribution Micro-Pal. Silurian Rocks of Can- 

 ada, p. 24. 

 1885. Solenopora compacta NICHOLSON and ETHERibuK. Geological Mag., dec. iii, vol. ii, p. 529. 



1888. Solenopora compacta NICHOLSON. Ibidem, vol. v, p. 15. 



1889. Solenopora compacta NICHOLSON. Manual of Paleontology, vol. i, p. 201, flgs. 83a-83d. 



Original description. " This species forms small sub-globular masses, from 1 to 2 

 inches in diameter. The concentric lamella 1 are thin and closely packed together, 

 there being in some specimens from 6 to 12 layers in the thickness of 2 lines." 



The internal structure is described by Dr. Nicholson as follows : " Composed of 

 radiating capillary tubes, arranged in concentric strata. The tubes vary from 



