572 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
1879. Glandula arenicola Verrill, Preliminary Check-list of Marine Inver- 
tebrates, p. 27. 
1879. Glandula arenicola Verrill and Rathbun, Proc. U. S. Nat. Mus., vol. 2, 
p. 231. 
1880. Glandula mollis Traustedt, Vidensk. Meddel. Naturhist. For. Kjoben- 
havn for 1879-1880, p. 420. 
1889. Glandida arenicola McDonald, Rept. U. S. Comm. Fish and Fisheries 
for 1886, p. 858. 
1891. Glandula arenicola + G. mollis Herdman, Journ. Linn. Soc. London, 
Zool., vol. 23, p. 582. 
1901. Glandula arenicola + G. mollis Whiteaves, Geol. Survey Canada, pub. 
no. 722, p. 267. 
1901. Glandula arenicola Kingsley, Proc. Portland Soc. Nat. Hist., vol. 2, 
p. 183. 
1909. Tethyum arenicolum + T. molle Hartmeyer, Zool. Anzeiger, vol. 34, 
p. 144, text-fig. 1-3. 
1909. Tethyum arenicolum + T. molle Hartmeyer, Bronn's Tier-reich, vol. 
3, suppl, pp. 1358, 1360. 
[Note. The "Glandula, species undetermined," recorded by Verrill and 
Smith (1873, pp. 502, 701) and Hartmeyer (1909a), from Vineyard Sound, 
10 to 20 fathoms, sand, may have been the young of this species. If not, it is 
uncertain what their species is. No specimens were found in the collections 
which were recognized as the ones referred to by Verrill and Smith.] 
Body ellipsoidal, sometimes nearly spherical, the small apertures 
(both square) situated rather near together on the anterior dorsal 
portion, either raised on conical papillae, or nearly level with the sur- 
face in contracted specimens. Test thin but tough, thickly and evenly 
coated with sand grains which adhere firmly. A few hair-like processes 
from the ventral region assist in anchoring the animal in the sand in 
which it lies buried, but it is not otherwise attached. Size of an aver- 
age specimen: 9 mm. long, 7 mm. deep, and 5 mm. to 6 mm. from side 
to side. Largest specimen about 14 mm. long. 
Musculature of mantle rather diffuse, transverse fibers predomi- 
nating. 
Tentacles, 32 or more, quite regularly arranged; 8 of the first, 8 of 
the second, and 16 of the third order. Fourth-order tentacles in a 
few of the intervals only. 
Dorsal tubercle C-shaped with the open interval directed to the 
left. Horns not incurved. 
Dorsal lamina plain, rather narrow. 
Branchial sac with four rather slight folds on each side, of which 
the second is more or less rudimentary. Internal longitudinal vessels 
