602 RITTER. 



Styela stimpsoni n. sp. 



(PL XVIIL, Fig. II and 12; and PI. XIX., Fig. 26; and PI. 

 XX., Figs. 27 and 28). 



General Appearance : Body irregularly oval ; narrow at the 

 anterior end where the siphons are placed ; the atrial at the 

 dorsal edge, and the branchial close to it, except in one specimen 

 where it is i.i cm. distant. Body sloping gradually from the 

 branchial siphon to the broad posterior end, where it is attached 

 by root-like processes of the test. Average length of four 

 specimens 3.2 cm., average of greatest diameter 3.1 cm. Siphons 

 prominent though often contracted ; both orifices four-cleft. 



Test : Over the greater part of the body, thin, leathery, usu- 

 ally smooth, or with wrinkles due to contraction. Color, in life, 

 as shown by Dr. Dean's figures, bright orange-red ; this, how- 

 ever, wholly destroyed in preserved specimens, the color here 

 being a light gray. Toward the posterior part the test becomes 

 thicker, firmer, crumpled, and furnished with numerous processes 

 and irregularities ; color of this part usually a dark brown, tinged 

 with yellow ; inner surface of the test, smooth, white, and shining. 



Mantle : Thick, composed of small but strong muscle fibers 

 very densely woven in the upper part, somewhat more loosely 

 woven in the lower part. Mantle closely attached to the bran- 

 chial sac by many strong vessels. 



Branchial Sac : Four folds on each side ; the two folds on 

 each side of the endostyle wath four to six bars ; the other folds 

 stronger with ten to fourteen bars ; four or five longitudinal ves- 

 sels between the endostyle and the folds on each side ; about six 

 vessels between the other folds ; transverse vessels of three sizes, 

 usually five or six medium-sized ones between two broad ones ; 

 the series of stigmata often crossed by small secondary' >'essels 

 which are sometimes incomplete. Meshes oblong with five to 

 seven long, rather narrow stigmata in them (PI. XIX., Fig. 26). 



Tentacles : Unbranched, very numerous, of three lengths, 

 about twenty long slender ones, with shorter ones alternating 

 with them, and very short ones alternating ^vith these, so that 

 there are three short tentacles between two long ones ; peripha- 

 ryngeal band close to the circle of tentacles. 



