S2 THE VOYAGE OF H.M.S. CHALLENGER. 



The Mantle is thin and membranous, and the musculature is extremely feeble ; with the 

 exception of a few bands radiating from the apertures, there are almost no muscular fibres. 



The Branchial Sac is strong, and not folded. The internal longitudinal bars are in 

 the form of broad ribbon-like bands. The transverse vessels are slight and irregular ; 

 narrow horizontal membranes are usually present. The infundibula are large, and are 

 usually square or pentagonal at the base. The fine interstigmatic vessels are narrow 

 and much coiled, the spiral having from ten to thirty turns (generally fifteen to twenty). 

 The radiating vessels are slight, a few short intermediate ones are frequently present. 



The Dorsal Lamina is a plain broad membrane. 



The Tentacles are branched and delicate ; they are numerous, about twelve large and 

 twelve smaller, and three orders of simple and very minute ones alternate regularly. 



Tlie Dorsal Tubercle is simple, having an elongated oval cavity ending in a quad- 

 rangular aperture anteriorly. It is placed in a shallow triangular peritubercular area. 



This is the fourth species of Eugyra known to science, the three others being Eugyra 

 glutinans, Moller ( = Eugyra arenosa, Alder), Eugyra pilularis, Verrill, and Eugyra 

 globosa, Hancock. The discovery, so far south as Kerguelen Island, of a member of this 

 genus, which has been hitherto found only in the northern hemisphere, is very 

 interesting. 



This species, though having all the characters of Eugyra well marked, differs from the 

 three previously known species in many particulars. Perhaps the most notable difference 

 is in the external appearance, as Eugyra kerguelenensi-s has a debcate transparent test 

 with no adhering sand, and has the atrial aperture permanently projecting on a short 

 cylindrical siphon (PL VI. figs. 4 and 5). The specimen represented in figure 5 differs 

 considerably from what is probably the normal condition of the species as shown in 

 figure 4. In internal structure, however, they are identical, and undoubtedly belong to 

 the same species. Probably figure 5 is a somewhat abnormal specimen. 



The mantle is remarkably thin, and, with the exception of the bands radiating from 

 the apertures, there are almost no muscles, only a few delicate fibres being placed at 

 considerable distances. 



The shallow infundibula in the branchial sac (PI. VI. fig. 8) are large and have a great 

 number of coils in the spiral ; up to thirty have been found, but the usual number is 

 between fifteen and twenty (PI. VI. fig. 8). Besides the delicate radiating vessels which 

 extend from the angles into the centre of the infundibulum, there are usually present 

 some intermediate ones of shorter extent (PI. VI. fig. 8, r.v'.). 



The tentacles are delicate but very numerous. There are five distinct sizes, the 

 two larger of which are always compound, and the three smaller usually simple (PL VI. 

 fig. 6). If we number them from A to E, according to their size, the arrangement will be 

 found to be as follows :— A, E, D, E, C, E, D, E, B, E, D, E, C, E, D, E, A (PL VI. 



