. Bulletin - United States National Museum. Science. 14 BULLETIN 115, UNITED STATES NATIONAL MUSEUM. the few massive appendages of the H. discus. It is in this respect strikingly similar to Strotocrinus, which with a greatly expanded calyx has similar small arms, in accordance with the fact, frequently observed in crinoids, that increase in size of calyx is often accompa- nied by a diminution in size of the arms. The interbrachial plates are few and large, usually in three ranges of 1—2—1 in the interray, and 2, exce])tionally 3, in single series in the second axils, with an occasional plate i
. Bulletin - United States National Museum. Science. 14 BULLETIN 115, UNITED STATES NATIONAL MUSEUM. the few massive appendages of the H. discus. It is in this respect strikingly similar to Strotocrinus, which with a greatly expanded calyx has similar small arms, in accordance with the fact, frequently observed in crinoids, that increase in size of calyx is often accompa- nied by a diminution in size of the arms. The interbrachial plates are few and large, usually in three ranges of 1—2—1 in the interray, and 2, exce])tionally 3, in single series in the second axils, with an occasional plate in the third. The anal interradius has usually an extra plate in the second range, but this ma}' sometimes also occur in other interradii, so the differentiation is not certain. The column of this genus partakes of a peculiar structure, more fully to be described under Dolatocrinus, whereby the nodal colum- nals are remarkably conspicuous, having a flanged peripheral rim overhanging and some- times concealing the adjoining internodals, and being studded in varying number with projecting cogs resembling fins, while the in- ternodals are thin and of less diameter. Fig. 6.—Distribution of arms a ii • • i j* ™ . oo u IN HiMERocRiNus ^^ ^^^ spccimeus, mcludmg some 23 show- ing the basal cone only, in addition to the 20 above mentioned, seem to belong to the type species, with the possible exception of one. "Hall's Coronocrinus, from the Manlius of New York, should be compared with this genus. Horizon and locality.—The type and only described species is from the Onondaga (Jeffersonville) limestone, at Louisville, Kentucky. Genus TECHNOCRINUS Hall. TECHNOCRINUS NIAGARENSIS, new species. Plate 5, figs. 1, 2. Among collections made for me in western Tennessee in recent years are two forms belonging to the group under consideration, the occurrence of which carries the age of their genera back to earlier epochs than hitherto known. TecTinocrinus is typically an Oris
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