VAN NAME: COMPOUND ASCIDIANS. 371 
distinguished mainlv by a reddish or yellow color. In his later works, 
the last mentioned form is regarded as only a variety of the former. 
But the type specimens of both are alike in every respect, the colors, 
of course, having long since faded out. The name luteolum must 
therefore be regarded as strictly synonymous with the name albidum, 
and should be entirely abandoned. The matter is comj)licated, how- 
ever, by the fact that two distinct forms have been confused under the 
name albidum (or luiednm, if the specimen happened to be of a reddish 
or yellow color). One of these, the true albidum (Verrill's type), is 
found chiefly north of Cape Cod, and is in this paper placed in the 
genus Tetradidemnum (see p. 377). The other species, more southern 
in its distribution, is a typical Didemnum [Leptoclinum]. Until 
better descriptions and figures of related species of other regions 
shall be available it seems best to treat it as a distinct and new 
species, a course which the constancy of its characters may after all 
eventually justify, even though the differences from related forms are 
small. 
Didemnum lutarium sp. nov. 
Text-figs. 8, 9; PI. 37, fig. 7. 
1869. Didemnium sp.?, Perkins, Proc. Boston Soc. Nat. Hist., vol. 13, p. 160. 
1871. Leptoclinum albidum (part.) + Leptoclinum luteolum (part.) Verrill, 
Amer. Journ. Sci., ser. 3, vol. 1, p. 446. 
1872. Leptoclinum albidum (part.) + Leptoclinum luteolum (part.) Verrill, 
Amer. Journ. Sci., ser. 3, vol. 3, p. 212. 
1873. Leptoclinum albidum (part.) + Leptoclinum luteolum (part.) Verrill 
and Smith, Report on Invertebrate Animals of Vineyard Sound, pp. 
403 (411, 424), 515, 706. 
1879. Leptoclinum albidum + L. cdbidum, var. luteolum Verrill and Rathbun, 
Proc. U. S. Nat. Mus., vol. 2, p. 231. 
1879. Leptoclinum albidum (.part.) + Leptoclinum albidum var. luteolum 
(part.) Verrill, Preliminary Check-List of Marine Invertebrata, p. 27. 
1886. Leptoclinum albidum (part.) -|- L. albidum var. luteolum (part.) Herd- 
man, Report Voyage Challenger, vol. 14, p. 287 and ff. 
1889. Leptoclinum albidum + L. albidmn var. luteolum McDonald, Rep. 
U. S. Comm. Fish and Fisheries for 1886, p. 858. 
1900. Leptoclinum albidum (in part, at least) Metcalf, Zool. Jahrljiicher, 
Anat., vol. 13, pp. 527, 562, 563, pi. 37, fig. 50 (neural gland, etc.). 
1902. Leptoclinum. luteolum Van Name, Trans. Connecticut Acad. Sci., 
vol. 11, p. 363. 
The colony in this species often becomes considerably over 100 mm. 
