Part II. -DESCRIPTIVE. 



DIPLEUROSOMA, genus nov. 

 DIAGNOSIS OF THE GENUS. 



Colony bilaterally symmetrical with reference to one of the planes that pass through the 

 principal axis, la cross section the colony is elliptical, with the common cloaca, or central 

 chamber, reduced to a narrow slit in the long axis of the ellipse. 



DIPLEUROSOMA ELLIPTICA, nov. sp. 



Figures 4, 5, tf, 7, and 8. 



DESCRIPTION OF THE SPECIES. 



Distribution. — Found in the Gulf Stream off Beaufort, North Carolina. It is, no doubt, 

 widely distributed in the waters of the Gulf Stream. 



Length if colony. — Twenty-two centimeters. 



Greatest diameter of colony. — Fifty-seven millimeter-. 



Least diameter of colony. — Twelve millimeters. 



Ratio between tin long axis and tht short axis of tht elliptical cross section. — About one to 

 four. 



Distribution of the ascidiozooids. —Regularly verticillated in small colonics, irregular in large 

 ones. 



Outer surfact of mantle. — Smooth in young colonies, thickly set in large ones, with 

 tubercles that are very variable, usually conical and symmetrical but often with a tongue-like 

 projection on the dorsal side. 



Oral tube. —Conical, axial, nearly as wide as long. 



Mouth. — In long axis and usually horizontal or at right angles to the long axis. In young 

 colonies, and in many of the zooids of large colonies, it is at the bottom of a shallow conical pit. 

 In most of the ascidiozooids in large colonies it is at the end of a conical process; in a few, on 

 the ventral surface and near the tip of a tongue-shaped process. 



Branchial chamber.— Not narrowed at inner end. 



QUI slits. — Thirty-seven or more. 



Longitudinal folds of branchial rhumhi-r. — Eighteen or more. 



Endostyle. Nearly straight. 



Testis. — In a pouch that protrudes beyond the general outline, with from seven to nine lobes. 



< 'loacal nvuscli . Long. 



Dorsal tentacles of pharynx. — About seven, variable and irregular. 



Oral processes. — The writers on Pyrosoma attribute great taxononiic importance to the 

 absence or presence or shape of the oral processes on the outer surface of the colony, since these 

 structures arc conspicuous when present and easy to sketch and to describe. 



In many species they are. no doubt, characteristic, affording a ready means of identification, 

 hut in others they are too irregular and variable to have any systematic value. 



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