3. Tristephanium hertwigii, Haeckel.
Acanthodesmia hertwigii, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. pp. 499, 539, Taf. xxxii. figs. 9a-9c.
Sagittal ring ovate or nearly semicircular; its dorsal rod straight, smooth (fig. 9c, a), its ventral rod (b) curved, thorny. Frontal ring much larger, thorny, violin-shaped, with a slight sagittal constriction. Basal ring smaller than the sagittal ring, thorny, kidney-shaped, with four different gates; the two cardinal pores much larger than the two jugular pores. (The four basal pores are often much larger than in the specimen figured by Bütschli. Also the number, form, and size of the spines is very variable.)
Dimensions.—Height of the frontal ring 0.07 to 0.09, breadth 0.17 to 0.2.
Habitat.—Fossil in Barbados.
Subgenus 2. Tristephaniscus, Haeckel, 1881, Prodromus, p. 445.
Definition.—Sagittal and frontal ring of equal size and form.
4. Tristephanium quadricorne, n. sp. (Pl. [93], fig. 7).
Sagittal and frontal ring of equal size and form, larger than the circular basal ring. From the four corners, in which the latter crosses the two former, arise four strong, divergent spines, branched like a deer's antler. Some smaller spines are scattered on the rings, and a bunch of four spines arises on the apical pole. The four upper gates are triangular, the four lower nearly semicircular, the latter of equal size, half as large as the former.
Dimensions.—Height of the frontal ring 0.13, breadth 0.14.