REPORT ON THE TUNICATA. 153 



The Branchial Sac has two distinct folds upon each side near the dorsal edge, 

 and one or two more indistinct ones ventrally. The transverse vessels are all of one 

 size. The internal longitudinal bars are numerous. The meshes are slightly elongated 

 antero-posteriorly, contain each four or five stigmata, and are divided transversely here 

 and there by a membrane. 



Tlie Dorsal Lamina is plain, and has no ribs nor teeth. 



Tlie Tentacles are larger and smaller alternately. The larger ones are short and 

 stout. 



The Dorsal Tubercle is a simple elliptical tubercle, with no visible markings. 



This species (PL XVIII. fig. 1, the upper specimen) was obtained, along with Styela 

 bythia, from 2600 fathoms. Although the two species are not unlike in external appear- 

 ance, they differ greatly in their internal structure. Styela bythia has four well-marked 

 folds upon each side of the branchial sac, while in Styela squamosa only two are distinct 

 upon each side, the others being in a rudimentary state. 



Then again the internal longitudinal bars in Styela squamosa, through broad and flat 

 as in Styela bythia, are not nearly so numerous as in that species (compare figs. 2 and 6 

 on PL XVIIL), and consequently the meshes are not so narrow, and usually contain four 

 or five stigmata in place of one or two. On the folds, however, they are of course more 

 closely placed, and there the meshes are more nearly of the size found in Styela bythia 

 (PL XVIIL fig. 4, br.f.). The meshes next the dorsal lamina contain each eight to ten 

 stigmata (PL XVIIL fig. 5). 



The dorsal lamina also differs from that of the last species, as it is a plain 

 membrane with no ribs or other markings, and with no marginal teeth. (PL XVIIL 

 fig. 5, d. I). The tentacles (PL XVIIL fig. 3) are of two sizes, but both are small. 



This species was obtained along with the last at Station 160 ; March 13, 1874 ; lat. 

 42° 42' S., long. 134° 10' E.; depth, 2600 fathoms ; bottom temperature, 0°"2 C; bottom, 

 red clay. 



Styela grandis, Herdman (PL XIX. figs. 1 and 2). 



Styela grandis, Herdman, Prelim. Rep., Proc. Roj'. Soc. Edin., 1880-81, p. 67. 



External Appearance.— -The shape is irregularly pyriform, the anterior end being- 

 large and somewhat globular, whfle the posterior narrows into a short thick stalk, by 

 which the animal is attached. The ventral edge is straight or slightly concave ; the dorsal 

 is long, and strongly convex. The branchial aperture is a little to the ventral edge of the 

 anterior end, and is directed ventrally ; the atrial is on the dorsal edge, about two-thirds 

 of the way from the anterior to the posterior end, and is directed dorsally and slightly 

 anteriorly. Both apertures are sessile; they are not very distinctly lobed, but are 

 conspicuous. 



