MOLGULA. 21 



Ocnus MOLGULA, Forbks. 



Body more or less globular, attached or free ; test membranous, 

 usually invested with extraneous matter ; orifices on very con- 

 tractile, naked tubes, the oral six-lobed, the anal four-lobed. 



The species of Mohj;ula have been found between tide-marks in 

 the laminarian zone, and as deep as twenty-five fathoms. The 

 surface is usually covered with particles of sand and other sul> 

 stances. Except in the number of lobes in the oral aperture, 

 Glandula of Stimpson does not seem to differ from this genus. 



Molgula arenata. 



Molgu'a arenata, Stimpso.v, Proc. Bost. Soc. N. II. iv. 230 (1852) ; Check Lists, 2 (1860). 



Body somewhat compressed laterally. Test thin, uniformly cov- 

 ered with coarse sand, which adheres very strongly. Apertures 

 small, on very short tubes, far removed from each other. Length, 

 three fourths of an inch. 



It inhabits the region of Nantucket and Martha's Vineyard. 

 (^Stimpsoa.) 



Molgula producta. 



Plate XXII. Figs. 315, 316. 

 Mo'gula producta, Stimpson, Proe. Bost. Soc. N. H. iv. 229 (1852) ; Check Lists, 2. 



This species is usually perfectly globular, while the apertures 

 are on tulles often equal in length to the diameter of the body, 

 which originate close together and diverge. The test is rather 

 thin, pellucid, usually of a pale rose tint, and covered, the tubes 

 included, with a thin coating of sand. The branchial aperture is 

 rounded, with six short cirrhi within ; the anal is square. Diam- 

 eter, half an inch. 



It occurred on a sandy bottom, in six fathoms, in Boston Bay, 

 and also at low water on Bird Island. The tadpole-like young 

 were ejected in August, and were of a light vermilion color, which 

 continued for a long time after their final detachment. (^Stimpson.) 



The drawing by Mr. Burkhardt, which I have referred to this 

 species, differs in color from Dr. 8timpson's description. The 

 details given by Mr. Burkhardt's drawings show the apertures to 

 correspond with the generic description of Molgula. 



