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adheres to fragments of shells and often to other Ascidians. It 

 resembles a species which I received from Europe under the 

 name of A. mentula^ but does not agree with the descriptions of 

 that species. 



A. GEOMETRicA. Body adhering by a broad base, depressed, 

 oval. Test thin, smooth, transparent, very pale greenish, with 

 an almost peripheric, narrow, dark-colored line or ridge, like a 

 fibre, from which other lines of the same character proceed, 

 dividing the surface into ten irregular polygons, two of which, 

 separated from each other by a third, contain the apertures. 

 These two polygons are wheel-like, being radiated with six 

 spokes from a centre, which is the sessile aperture. Proceeding 

 from, and perpendicular to each of the dark lines, are bright 

 straw-colored fibres, extending toward the centres of the poly- 

 gons but not reaching them. Length, half an inch. 



Dredged in forty fathoms on a muddy bottom off Long Island, 

 Gr. Manan. One specimen only was found, which was adhering 

 to a dead valve of Pecten Magellanicus. 



MOLGULA. 



M. soRDiDA. Body small, globular, usually covered with 

 mud or sand ; color, when clean, pale white. Test thick and 

 smooth, except around the apertures, where it is wrinkled trans- 

 versely, and provided with as many longitudinal ridges as there 

 are rays in the aperture. Tubes prominent, near together. Bran- 

 chial aperture provided with six tentacular filaments, projecting in- 

 wards, corresponding with its six rays. The anal tube is longest, 

 and its four ridges, corresponding with the four rays of its aper- 

 ture, are very prominent. Branchial sac with fourteen plications. 

 Diameter half an inch. 



This species is found at low water in Charleston Harbor, S. C. 

 among the sediment and parasitic corallines and plants which 

 incrust the rocks of the breakwaters. 



M. PRODUCTA. This species is usually perfectly globular, 

 while the apertures are on tubes 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 



