Cyathocormus mirabilis n. g., n. sp. lg 



with the anterior extremity of the endostyle and the dorsal tubercle 

 respectively. By tracing the ridge ventrally it is found to be 

 directly continuous with the ciliated band on the inner surface of 

 the ]ip of endostyle. Near the dorsal end the ridge forms the 

 greater part of the side wall of the dorsal tubercle and gradually 

 disappears towards its free extremity. The cells composing the 

 ridge are high and columnar, and the cilia are very short through- 

 out. 



Dorsal tubercle. This organ is placed at the anterior end of 

 the dorsal edge of the branchial sac, and is very conspicuous on 

 account of its unusually large size. As shown in PL IL, figs. 8 and 

 10, it projects into the branchial cavity just below the base of the 

 branchial siphon on the dorsal side and is clearly visible from 

 outside when the branchial orifice is moderately open. It is 

 conical in shape, with blunt apex, and attached obliquely to the 

 anterior wall of the thorax in such a manner that the apex is 

 directed towards the axis of the body. The aperture of the 

 neural gland is situated on its anterior surface about half way 

 between the apex and the base of the organ where it joins the base 

 of the median dorsal tentacle (PI. II., fig. 10). The aperture is 

 simple, oval in outline, and is placed transversely in reference to 

 the axis of the organ. As the peripharyngeal ridge is continuous 

 with the ciliated patch covering the apex of the dorsal tubercle, 

 and the peripharyngeal membrane almost reaches the anterior 

 surface of the organ before it is lost to sight, these two components 

 of the peripharyngeal band well deserve the names of "anterior 

 and posterior lips' ' , as they are sometimes called in simple ascidians. 

 At the apex and on both sides the wall of the organ is made up 

 of cubical or columnar cells. In the immediate neighbourhood of 

 the aperture the cells are rather high and ciliated. In other 

 places the tubercle is covered with an epithelium of flattened 

 cells. 



Nerve ganglion. The nerve ganglion is in its usual position on 

 the dorsal side of the branchial sac immediately beneath the ecto- 

 dermal epithelium of the body wall. It is oval or elliptical in 

 outline and sends out nerve trunks both anteriorly and posteriorly. 



