BIOLOGICAL EESULTS OF THE "ABGO" CRUISE. 207 



The Mantle is thin, and has the usual niolgulid fusiform 

 muscles, which, however, are feebly developed. The 

 sphincters are strong (PI. IX., figs. 5 and 6). 



The Branchial Sac has six folds on each side. There are 

 five internal longitudinal bars on a fold. The stigmata 

 are, in most places, not much curved, and run in the main 

 antero-posterioiiy. There are occasional wide transverse 

 vessels with broad horizontal membranes, which, with the 

 branchial folds, form large meshes crossed by smaller and 

 more irregularly placed horizontal membranes. These 

 meshes are about twice as long as they are broad (PL IX., 

 fig. 7). 



The Dorsal Lamina is a plain membrane. 



The Tentacles are of two sizes, 5 large and 5 small. They 

 are bipinnate (PL IX., fig. 8, tn.) 



The Dorsal Tubercle is linear and undulating, with its 

 ends slightly coiled. 



The Alimentary Canal is long, and is recurved so that 

 the intestinal loop comes close to the atrial aperture. 



The Reproductive Organs are developed on both sides. 

 Each forms an elongated sausage -like yellow mass. 



This specimen had about 20 copepoda (Notodelphis 

 agilis, both males and females,) in its branchial sac, four 

 or five of them with egg masses. 

 Poly car-pa argoensis* n. sp. (PL IX., figs. 1 — 3). 



External appearance. — The body is erect and elongated 

 antero-posteriorly. It is scarcely compressed, and is 

 attached by the posterior end and a small area at the end 

 of the right side (see PL IX., fig. 1). The anterior end is 

 rather wider than the posterior, and bears the two aper- 

 tures on prominent siphons. The branchial aperture is 

 terminal while the atrial is a little way down the dorsal 

 edge ; both are distinctly four-lobed. The surface is even 

 * From the ship "Argo." 



