400 W. G. Van Name — Bermuda Ascidians. 



Ascidia curvata Traustedt. 



Ascidia curvata Traustedt, Vestindiske Ascidia? Simplices, Aftryk af Vidensk. 

 Meddel. fra den naturh. Foren. i Kjobenhavn, p. '25. pi. iv, figs. 8, 9, and 

 10, and pi. v, fig. 19,1881. 



Plate LVI. Figures 80, 81 and 82. Plate LXIII. Figures 145and 146. 



The body is much more elongated than in the last species and 

 tapers gradually toward the anterior end. It is strongly flattened 

 laterally. The atrial siphon is generally situated behind the middle 

 of the body Both siphons are usually long and often turned to the 

 right, the animal being generally attached by the entire left surface. 

 Great variations in the external form of the body are common. The 

 largest specimen measures about 50 mm in length and half as much in 

 a dorso-ventral direction. 



The test is greyish or practically colorless and transparent, soft 

 and gelatinous, moderately thick on the right side but very thin and 

 easily torn on the left side. Its surface may be smooth and glossy, 

 allowing much of the internal structure to be seen, or it may be 

 wrinkled or in some cases so incrusted with sand and shell fragments 

 that nothing can be seen through it. The apertures generally have 

 about the number of lobes characteristic of the genus, but they are 

 not readily counted in the contracted state of the orifices. There 

 are markings of light orange brown about the apertures in the living 

 animal. 



The mantle is very delicate and transparent. On the right side 

 there are numerous but very slender muscle-bands, mostly transverse 

 or only slightly oblique. They taper off and end soon after passing 

 the median line on the dorsal and ventral surface, leaving the left 

 side practically free from muscle bands except the sphincter muscles 

 of the siphons, which are composed of similar delicate bands placed 

 close together. Very few longitudinal bands are present. 



The tentacles are numerous and placed close together, slender and 

 uniformly tapering, of several sizes. The dorsal tubercle is small, 

 U-shaped. 



The branchial sac extends for a long distance behind the oesopha- 

 geal opening. Its internal longitudinal bars are separated by 4 or 

 5 stigmata ; 8 or 10 stigmata intervene between the dorsal lamina 

 and the first bar on each side of it. In some places the transverse 

 vessels are nearly equal in size, in other parts (especially in the pos- 

 terior portion of the sac) they show more or less tendency to alter- 

 nate in size. Very large vessels, such as are shown in Traustedt's 



