REPORT ON THE TUNICATA. 161 



ally; the anterior end is convex; the dorsal and ventral edges are free and rounded. 

 The body is attached by the posterior end and half of each side to a piece of coral. The 

 apertures are sessile, four-lobed, and moderately far apart ; they are placed at the opposite 

 ends of the anterior extremity. 



The surface of the test is flat, but is minutely scaly ; these scales are largest and 

 most distinctly marked around the apertures. The colour is light yellow, with a brownish 

 tinge at the apertures, and is white on the area of attachment. 



Length (antero-posterior), 1'6 cm.; breadth (from side to side), 2*4 cm.; thickness 

 (dorso-ventral), 2 cm. 



The Test is thin, but very tough ; it is opaque, and is white and glistening on the 

 inner surface. 



The Mantle is rather thin ; the muscular bands are numerous, but very fine. 



The Branchial Sac has four folds upon each side. These are very slight, being merely 

 the approximation of a number of internal longitudinal bars. There are about ten bars 

 at these places, and ten in the intermediate opener parts. The meshes are square 

 or elongated antero-posteriorly, contain each four stigmata, and are divided each into 

 two areas by a narrow transverse membrane. 



The Dorsal Lamina is ribbed transversely, and is slightly toothed at the edge. 



Tlie Tentacles are simple and of three sizes; there are fifteen large, fifteen small, and 

 about thirty very minute ones, placed alternately. 



Tlie Dorsal Tubercle is placed at the bottom (posterior extremity) of a rather deep 

 peritubercular area ; it is small and irregular in shape 



This is in some respects rather an abnormal Styela. It is elongated laterally and 

 depressed, thus forming a wide convex anterior extremity (PI. XX. fig. 1), upon which 

 the small cross-slit branchial and atrial apertures are placed. 



The surface of the test is modified into a series of small polygonal areas, winch give it 

 a scaly appearance. Each of the rounded or polygonal areas is marked by a series of 

 roughly concentric lines (PL XX. fig. 2), something like what Heller figures 1 in the 

 case of Cynthia dura. The mantle is thin, but the muscle bands are \ • i y numerous. 

 They are delicate and are placed irregularly, running in all directions and forming a close 

 network (PI. XX. fig. 3). 



The branchial sac has the folds in a rudimentary state, and formed merely by the 

 crowding together of the internal longitudinal bars along certain areas. In these 

 regions the meshes are of course very narrow (PI. XX. fig. 4, br.f.), while in the 

 intermediate spaces they are rather wide, and contain each four large stigmata. The 

 endostyle is conspicuous in this species ; it is wider than usual, and is of a reddish brown 

 colour. 



1 Untersuchungeii li. J. Tun. des a<lriut. Meerea, Abth. 3, pi. iii. fig. 3. 



