These statements are based on the author's observations of the animal in the Bay of Fundy in 1900.
Lovén, "On a recent Form of Echinoconidae," Bih. Svenska Akad. Hand. xiii. Af. 4, No. 10, 1889.
Details were given to the author in conversation with Dr. Robertson in 1896.
This family includes three families discriminated by Meissner (Bronn's Thier-Reich, vol. ii. Abt. 3, Buch iv. "Die Seeigel," 1904, p. [402]), viz.: Ananchytidae, Pourtalesiidae, and Urechinidae. They only differ in the pores for the tube-feet, which are paired in the first, slit-like and single in the second, and single in the third.
"On Silurian Echinoidea and Ophiuroidea," Quart. Journ. Geol. Soc. lv. 1899, pp. 701 et seq.