80 THE PALEONTOLOGY OF MINNESOTA. 
{[Solenopora. 
“The radiating canals are a little smaller than in the common H. spheroidalis 
Dunean, of the Niagara, being as a rule not over 0.27 mm. in diameter. H. inequalis 
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 Keutucky, Tennessee, 
Wisconsin, and Minnesota, the localities from which Mr. Ulrich obtained his mate- 
rial, should not at present be regarded as belonging to Microspongia 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.—Rare 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. 
Collectors—W. H. Scofield, E. O. Ulrich and C. Schuchert. 
Mus. Reg. No. 7711. f 
? Class HY DROZOA. 
?Sub-Class H YDROIDA. 
SOLENOPORA, Dybowski. 
SoLeNoporA compacta billings. 
PLATE F, FIGS. 21-23. 
1862. Stromatopora compacta BILLINGs. Paleozoic Fossils, vol. i, pp. 55, 210. 
? 1877. Tetradium peachti NICHOLSON and ETHERIDGE. Annals and Magazine of Natural History, 
ser. iv, vol. xx, p. 166. 
? 1877. Solenopora spongioides DyBowski. Die Chetetiden der ostbaltischen Silur Formation, 
p. 124, pl. 2. 
1879. Solenopora(?) compacta DAWSON. Quart. Jour. Geological Society, London, vol. xxxv, p. 53. 
1883. Tetradium peachii, var. canadense Foorp. Contribution Micro-Pal. Silurian Rocks of Can- 
ada, p. 24. 
1885. Solenopora compacta NICHOLSON and ETHERIDGE. Geological Mag., dec. iii, vol. ii, p. 529. 
1888. Solenopora compacta NicHOLSON. Ibidem, vol. v, p. 15. 
1889. Solenopora compacta NICHOLSON. Manual of Palwontology, vol. i, p. 201, figs. 88a-83d. 
Original description. This species forms small sub-globular masses, from | to 2 
inches in diameter. ‘The concentric lamelle 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 
