494 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Caesira crystallina (Moller). 
PI. 48, fig. 31-33; text-figs. 12, 13. 
1842. Clavelina crystallina Moller, Naturhist. Tidsskr., vol. 4, p. 95. 
1852. Pera pellucida Stimpson, Proc. Boston Soc. Nat. Hist., vol. 4, p. 232. 
1860. Pera pellucida Stimpson, Smithsonian Check-list, p. 1. 
1870. Pera pellucida Binney, Gould's Invertebrata of Massachusetts, ed. 
2, p. 17. 
1872. Pera crystallina Verrill, Amer. Journ. Sci., ser. 3, vol. 3, pp. 213, 290, 
pi. 8, fig. 9. 
1879. Pera crystallina Verrill, Preliminary Check-list of Marine Inverte- 
brates, p. 27. 
1891. Pera chrystallina Herdman, Journ. Linn. Soc. London, Zool., vol. 23, 
p. 565. 
1901. Pera crystallina Whiteaves, Geol. Survey Canada, pub\ no. 22, p. 271. 
1903. Molgula crystallina Hartmeyer, in Romer and Schaudinn, Fauna 
Arctica, vol. 3, p. 137. 
1905. Molgula crystallina Bjerkan, Bergens Mus. Aarbog, 1905, no. 5, p. 4. 
1906. Molgula crystallina Redikorzew, Trav. Soc. Nat. St. Petersbourg, 
vol. 37, pt. 1, p. 309. 
1907. Molgula crystallina Redikorzew, Ann. Mus. Zool. Acad. St. Peters- 
bourg, vol. 11, pp. 128, 151-153. 
1907. Molgula crystallina Redikorzew, Zool. Anzeiger, vol. 31, p. 521. 
1908. Molgula crystallina Redikorzew, Trav. Soc. Nat. St. Petersbourg, 
vol. 39, pp. 20, 22, 42. 
1908. Molgula crystallina Bjerkan, Tromsoe Mus. Aarshefter, no. 25, pp. 56, 
114. 
1908. Molgula crystallina Redikorzew, Mem. Acad. Imp. Sci. St. Peters- 
bourg, cl. phys.-math., vol. 18, no. 11, p. 11, pi. 1, fig. 2. 
1909. Caesira crystallina Hartmeyer, Bronn's Tier-reich, vol. 3, suppl., 
p. 1323. 
1912. Caesira crystallina Hartmeyer, Sitzungsb. Ges. Naturforsch. Freunde, 
1912, no. 1, p. 14. 
The following notes on the structure and the illustrations were made 
from only two specimens, but one of which was dissected. 
Body ovoidal, tapering more or less abruptly at one end into a 
narrow pedicel (which may be nearly as long as the body) by which 
the animal is attached. Apertures not very prominent; branchial 
situated on one side of the body, six-lobed; atrial situated at end oppo- 
site origin of pedicel, four-lobed. Surface of body fairly smooth, 
with a few slight wrinkles but no processes or adhering foreign matter. 
Neither specimen much exceeded 20 mm. in length including the 
pedicel, which was 6 mm. to 8 mm. long. The species attains, how- 
