ASCIDIANS OF THE PHILIPPINES VAN NAME. 



87 



71883. Styela plicata Tbaustedt, Vidensk. Meddel. Naturh. For. Kjoben- 



havn, ann. 1SS2, p. 123, pi. 5, figs. 6, 1G. 

 1878. Styela areolata Heller, Sitz.-Ber, Akad. Wiss. Wien, vol. 77, p. 10S, 



pi. 2, fig. 14. 

 1906. Styela areolata Herdman, Ceylon Pearl Oyster Fisheries. Special 



Rep. No. 39, p. 316, pi. 4, figs. 24-33. 

 1909. Tethyum areolatum Hartmeyer, Broon's Tier-reich, vol. 3, suppl., 

 p. 1358. 



The following description has been prepared from the specimen 

 from station D5147 (Cat. No. 5930, U.S.N.M.) (see below), as it 

 is the only one having the reproductive organs developed. 



Body irregularly oblong or roughly cylindrical slightly curved, 

 tapering abruptly at the anterior end and attached obliquely by the 

 posterior part. Branchial aperture four-lobed, nearly terminal; 

 atrial aperture probably also four-lobed, situated only a little way 

 back on the dorsal side. Test rather thick and soft though tough, 

 whitish externally 

 with a slightly pearly 

 lining; outer surface 

 into irregu- 



raised 



larly rounded eleva- 

 tions of different 

 sizes near the aper- 

 tures, but smoother 

 though not shiny on 

 the posterior and ven- 

 tral portions. Length 26m., 

 14m. ; lateral diameter about the same. 



Mantle muscles fairly well developed; the superficial layer, con- 

 sisting chiefly of circular and transverse fibers, forms a practically 

 continuous sheet, especially on the dorsal and anterior parts; the 

 deeper layer, consisting largely of muscles radiating from the aper- 

 tures and extending down the sides, is gathered into bands. 



Tentacles net very numerous; apparently about 16 large ones 

 representing two orders and, in addition, smaller ones in some of 

 the intervals. 



Dorsal tubercle oval; its orifice horseshoe-shaped, with the open 

 interval (which is so narrow as to easily escape notice) directed 

 forward. 



Dorsal lamina plain. 



Branchial sac with four well-developed folds on each side. Four 

 or five orders of transverse vessels quite regularly arranged in some 

 places, the smallest crossing the stigmata. Internal longitudinal 

 vessels broad and flat, not very numerous; generally separated by 

 from five or six to eight or nine stigmata on the intervals between 

 folds. (Next to the endostyle there are often 12 or more stigmata 



Figs 38-40. — Styela areolata Heller. 38, Left and 

 right sides of body. natural size. 39, dorsal 

 tubercle. x 9. 40, dorsal end of a gonad. x 12.5. 



greatest dorso- ventral diameter, about 



