The Maquoketa Sliales. — James. 355 
curved, though the spechnens show little variation in size. It 
is about 10""" in length, and 1""" in diameter at the base, taper- 
ing to a sharp point. A slender groove extends along one 
side. Occasional specimens show what appear to be a series 
of joints. In section it is circular. It is so abundant as to 
make up certain layers of rock, and at times specimens are 
collected in groups as if swept together by currents and en- 
tangled in a mass. Should this prove to be a new species, I 
propose the name of lowaensis for it. 
Hyolithes 2^<^'''viuscidus Hall is interesting as belonging 
to a group which was largely developed in Cambrian time. It 
is associated in the same beds with the preceding, though not 
nearly so abundant. t is probably this form which was cata- 
logued^* as occurring at Cincinnati under the name of Hyolithes 
americana Billings. This is, however, a Cambrian form ac- 
cording to Walcott.^^ Mr. Walcott has described^" H. vanux- 
emi, from the Pogonip (Lower Silurian) of Nevada, which is 
possibly identical with Hall's species as above. In cross sec- 
tion, what appears to be a siphuncle, sub-central, is occasion- 
ally to be observed. 
Raphistoma viicula, Hall, originally described as Pleuro- 
toniaria micula, is in all probability the same as R. svbtilstria- 
tum from the Trenton of New York. A figure, but no descrip- 
tion of it, is given by Hall in the Geology of Wisconsin, p. 55, 
1862. A comparison of the Iowa specimens with forms from 
Cincinnati show that J?, micula occurs at Cincinnati, though 
it has been recognized under another name. In fact R. micula 
is a synonym for R. subtilstriatum. 
Orthoceras sociale, Hall, originally described as 0. grecjarium, 
was changed by professor Hall in Miller's catalogue Palaeozoic 
Fossils, p. 245, 1879. This was the only species of cephalopod 
found. The specimens vary from one-fourth of an inch to three 
inches in diameter. Only a few of the latter were obtained. 
Some of the smaller and better preserved specimens show trans- 
verse lines such as are seen in specimens of Endoceras protei- 
/brme,and as shown by figures given by professor Hall. In other 
specimens where the outer surface of the shell is worn off, the 
^*Ulrich,Cat. Foss. Cin. Group, 1880; also James, (J. F.) Cat. Foss. 
Cin. Group, 1886. 
2'Bull. U. S. Geol. Survey No. 30, p. 132, 1886. 
»»Mon. U. S.Geol. Survey, vol. 8, p. 85, 1884. 
