POLYCITOR (EUDISTOMA) MAYERI NOV. SP., FROM THE TORTUGAS. 



BY R. HARTMEYER. 



Among the ascidians I collected in 1907 at the Tortugas, and con- 

 cerning which I published a preliminary note in 1908 (Year Book Car- 

 negie Institution of Washington, No. 6, p. no), there is a new and very 

 interesting species of Polycitor, a genus not hitherto known, from the 

 West Indies. I name this new species Polycitor (Eudistomd) mayeri, in 

 honor of Dr. Alfred Goldsborough Mayer, director of the Department 

 of Marine Biology of the Carnegie Institution of Washington. 



Polycitor mayeri is the largest and most beautiful ascidian of the 

 Tortugas. It was collected in the deeper water of the Southwest Channel 

 near Loggerhead Key, on sandy or muddy bottoms, where it seems to 

 be fairly abundant and where it lives together with many other species 

 of ascidians, most of which are wanting on the reefs or in the shallow 

 water inside of the reefs. 



The colony varies in shape. It usually consists of a more or less 

 club-shaped mass (fig. i), supported by a short peduncle. There is no 

 distinct constriction at the (upper) distal end of the peduncle. Some- 

 times the colony forms an irregularly rounded or ellipsoidal mass, later- 

 ally little compressed, the area of attachment being broad. In one 

 case, the lower end is prolonged on one side to form a thin expansion 

 by which the colony probably was attached. In some cases two or three 

 masses of different sizes are united and attached by a common base. 

 In its variable shape Polycitor mayeri resembles Macroclinum pomum 

 (Sars). The length of the largest club-shaped colony is 70 mm., the 

 greatest breadth 35 mm., and the greatest thickness 27 mm. A smaller 

 one is 52 mm. in length, 27 mm. in greatest breadth, and 21 mm. in 

 greatest thickness. On the other hand, one of the rounded, broadly 

 attached colonies measures 30 mm. in length, 44 mm. in greatest breadth, 

 and 23 mm. in greatest thickness. There are some much smaller club- 

 shaped colonies in the collection, not over 20 mm. in length. 



The lower part of the colony, especially the peduncle, is incrusted 

 with sand grains, fragments of shells, small stones, serpula-tubes, etc. 

 The upper part of the colony is free from any foreign bodies, the surface 

 being perfectly smooth and glistening. 



The color is pale yellowish with a reddish or violet tint. Specimens 

 preserved in formalin have become milky -white ; alcoholic specimens are 

 more transparent, so that the ascidiozooids can be more or less distinctly 

 seen as yellow spots. 



The test is firm and cartilaginous; small sand grains are included 

 in the interior of the test, but not in great quantity. 



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