524 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
1879. Halocynihia echinala Verrill, Proc. U. S. Nat. Mus., vol. 2, p. 197. 
1879. Halocynihia echinala Verrill, Preliminary Check-list of Marine Inverte- 
brates, p. 27. 
1879. Halocynihia echinala Verrill and Rathbun, Proc. U. S. Nat. Mus., 
vol. 2, p. 231. 
1889. Halocynihia echinala McDonald, Rept. U. S. Comm. Fish and Fisheries 
for 1886, p. 858. 
1891. Cynthia echinala Packard, Labrador Coast, chap. 15, p. 396. 
1899. Cynlhia arclica + C. echinala Hartmeyer, Zool. Jahrbiicher, Syst., 
vol. 12, p. 468, fig. C; pi. 22, fig. 3; pi. 23, fig.s. 3, 11, 18. 
1900. Cynlhia echinala Metcalf, Zool. Jahrbiicher, Syst., vol. 13, p. 511. 
1901. Cynthia (Halocynihia) echinala Kingsley, Proc. Portland Soc. Nat. 
Hist., vol. 2, p. 183. 
1901. Cynthia echinala Whiteaves, Geol. Survey Canada, pub. no. 722, p. 268. 
1903. Halocynihia arclica + H. echinala Hartmeyer, in Romer and Schau- 
dinn. Fauna Arctica, vol. 3, pt. 2, pp. 190, 373, pi. 11, figs. 10, 11. 
1906. Halocynihia arclica Redikorzew, Trav. Soc. Nat. St. Petersbourg, 
vol. 37, pt. 1, pp. 154, 308, 310. 
1907. Halocynihia arclica Redikorzew, Ann. Mus. Zool. Acad. St. Peters- 
bourg, vol. 11, pp. 130, 151-153. 
1907. Halocynihia arclica Redikorzew, Zool. Anzeiger, vol. 31, p. 521. 
1908. Halocynihia arctica Bjerkan, Rept. Second Norwegian Arctic Exped., 
no. 14, p. 5. 
1908. Halocynihia arctica Redikorzew, Trav. Soc. Nat. St. Petersbourg, 
vol. 39, pp. 20, 23. 
1908. Halocynihia arclica Redikorzew, Mem. Acad. Imp. Sci. St. Peters- 
bourg, ser. 8, cl. phys.-math., vol. 18, no. 11, p. 26. 
1908. Halocynihia arclica Bjerkan, Tromsoe Mus. Aarshefter, no. 25, pp. 60, 
115. 
1909. Pyura arclica + Microcosnius echinalus Hartmeyer, Bronn's Tier- 
reich, vol. 3, suppl., pp. 1339, 1445. 
1910. Pyura echinala Hartmeyer, Sitzungsb. Ges. Naturforsch. Freunde, 
1910, no. 5, p. 231-240, pi. 8. 
1910. Pyura echinala Hartmeyer, Danmark-Expeditionen, vol. 5, p. 233. 
1911. Pyura arctica Redikorzew, Ann. Mus. Zool. Acad. Sci. St. Petersbourg, 
vol. 16, p. 216. 
1912. Pyura echinala Hartmeyer, Sitzungsb. Ges. Naturforsch. Freunde, 
1911, no. 10, p. 439. 
1912. Pyura echinala Hartmeyer, Vidensk. Meddel. Naturhist. For. Kjo- 
benhavn, vol. 63, p. 266. 
Body of elliptical outline when seen from one side, the antero- 
posterior diameter exceeding the others. Attachment usually by a 
comparatively small area on the ventral surface; body often slightly 
compressed in a dorso-ventral direction. Apertures four-lobed, 
on small conical papillae on the dorsal surface of the body; rather 
