24 University of California Piiblicaiions in Zoology. [Vol.4 



Benthascidia michaelseni, n- sp. 



PI. :2, figs. 24 to 30. 

 The two specimens secured were both too much mutilated to 

 permit clear recognition of what the general form of the body 

 was. Unfortunately too a number of important anatomical points 

 could not be made out with certainty. The description must 

 consequently be understood to be incomplete. The specimens 

 were curiously broken in almost exactly the same way. 



External Characters.— Long pedunculate, the peduncle being 

 smooth and column-like, thickest at base, gradually diminishing 

 in diameter for about a third of its entire length, then as grad- 

 ually increasing again to pass insensibly into the body (pi. 2, 

 fig. 24) . Length of the peduncle to where body thickening begins 

 about 220 mm. Base of peduncle rising abruptly from a mass 

 of fine short roots, or hold-fasts by which the animal was un- 

 doubtedly anchored to the bottom. Thickness of the peduncle 

 immediately above the roots about 30 mm. 



Form of the body undetermined, Init quite certainly no pro- 

 jecting siphons. Whole animal, both body and peduncle hyaline 

 to transparent, without pigment, the visceral mass showing 

 through distinctly. Test for the most part very thin and soft, 

 though thickened to 3 or 4 mm. on portions of the body, this 

 thickening not uniform but producing low nodulations in nearly 

 circular areas of sizes varying from a few mm. to 15 or 20 mm. 



3Iantle very thin and delicate, separating readily from the 

 test. Muscle fibers of the mantle arranged in delicate though 

 definite bands running generally in the same direction, hence 

 parallel with one another (fig. 26). These considerably stronger 

 and closer together in some portions of the animal than others, 

 though distribution of the heavier portions not determined. 



Branchial Apparatus. — Branchial orifice (without siphon) 

 very large, 35 mm. in diameter, circular and without lobes or 

 markings of any sort so far as ascertained. Atrial orifice not 

 found (apparently far remote from the branchial orifice). 

 Branchial tentacles minute and very numerous, three or four 

 hundred, simple but irregular in shape, many larger at the free 

 end and somewhat flattened. A great number of minute pro- 



