6 W. A. HKKDMAN. 



or less sqimrc niul lunnel-liko when the animal is nlivc and fully expauded. The 

 other anatomical characters are sufficiently shown in the figures on Plate I. or 

 descrilwd in the aViovc diagnosis. 



Styela rotunda. 

 (Plate VI., figs. 14-19). 



Localit;/. — Winter Quarters, in McMurdo Bay. 



Extenial Appearance. — Shape almost globular, attached hy a wide posterior end, 

 not flattened. Both apertures minute, cross-slit, inconspicuous, sessile, on the rounded 

 anterior end about 1 cm. apart. Surface even, hut finely roughened. Colour yellow. 

 Size 2 cm. dorso-ventrally x 1 • 8 cm. antero-posteriorly x 1 " 8 cm. from side to side. 



Test thin, hut leathery ; stiff", but not tough, easily torn. 



Mantle closely adhering to inner surface of test. 



Branchial Sac with four folds on each side, the ventral ones are the slighter and 

 placed further apart. Very many longitudinal bars arc present. There may be as 

 many as eight or ten on a fold, and about twenty to twenty-four in the interspace 

 (fig. 15). The transverse vessels are of three oi'ders, but none are very wide. The 

 me-shes are elongated vertically and contain two or three long narrow stigmata each. 

 They arc crossed by a fine horizontal vessel (fig. 15). 



Dorsal Lamina a narrow plain membrane. 



Tentacles simple, at least forty large and a few smaller scattered irregularly 

 between. 



Dorsal Tubercle simple, horse-shoe shaped, turned with the opening to one side. 



T/ie AUme)itary Canal is posterior to and partly on the left side of the branchial 

 sac. The stomach is long and is very finely ridged along its length (fig. 17). 



The Gonads are two or three narrow, yellow, convoluted tubes on each side. 



This s^iecies recalls in some respects the species of Dendrodoa from Arctic seas, 

 antl especially perhaps D. kuekenthali, Ilartmeyer, but differs in having gonads on 

 both sides of the body — a character which determines its position as a Styela. It 

 resembles in external appearance St. nordenskjoeldi, Michaelsen, from Magellan Strait 

 and other localities at the .south end of America, but differs wholly in the structure of 

 the bninchinl sac and other details of anatomy. The figure (Plate VI., fig. 14) is from 

 a photograph, and represents the specimen, of which the measurements are given above, 

 at double the natural size. A .second specimen slightly smaller, 1*8 x I'G cm., was 

 obtained from " Dredge off Coulman Island — 13. i. 02 — 100 fathoms." 



