REPORT ON THE TUNICATA. 63 



the nuclear thickening, and the greater part of one side of the body remains ; of the 

 mantle and the nucleus and other internal organs no traces are left. 



The figure (PI. IV. fig. 9) shows the specimen, about one half the natural size, with 

 the test restored as much as possible to its natural condition. The branchial aperture 

 is very large. Its dorsal and ventral lips are semicircular, and the opening measures 

 6 cm. from side to side. It is surrounded by a slightly thickened border (PI. IV. fig. 9). 

 The nuclear thickening of the test is placed very far back, close to the atrial aperture. 

 It is over 6 cm. in length antero-posteriorly. It is distinct, from its thickness and 

 smoothness, but is not so prominent as in the case of Salpa costata-tilesii (PL IV. 

 fig. 1, vise). The atrial aperture is diamond-shaped when seen from the posterior 

 end. It measures upwards of 2 cm. across. Its edges are thin, and are imj)erfect in 

 the specimen. 



The pointed tubercles scattered along the dorsal part of the test are exactly like 

 those which are found on the ventral surface in Salpa costata-tilesii (see PL lA'^. figs. 1 

 and 4). The ventral surface in the present specimen is perfectly smooth. The remark- 

 able tubular processes of the test which are found on the sides of the body are nearer 

 to the ventral than the dorsal edge. Two are placed near the middle of the body, and 

 two near the posterior end (PL IV. fig. 9), close to the nuclear swelling. The processes 

 are from 5 mm. to 1 cm. in extreme length, and their terminal openings are about 

 5 mm. in diameter. 



This species differs from the solitary form of Salpa costata-tilesii in its external 

 appearance, in the absence of any horn-like processes at the posterior end of the body, 

 in the position of the nuclear thickening of the test, in the position of the pointed 

 tubercles, and especially in the presence of the curious tubular projections on the sides 

 of the body. It, however, resembles the aggregated form of that species in which 

 there are no horns in some respects, but difi"ers in possessing the tubular appendages. 

 If these remarkable structures could be explained as being the modified remains of the 

 processes of the test which join the young aggregated forms together in the chain, then 

 I should be inclined to refer this specimen to Salpa costata-tilesii, aggregated form ; but 

 no traces of any such projections are to be seen in Traustedt's figures. It is evident 

 that the examination of further specimens is necessary, before this form can be referred 

 to its position with certaint}^ 



Salpa hexagona, t^uoy and Gaimard. 



Salpa hexagona, Quoy and Gaimard, Freycinet, Voyage, p. 505, 1824. 

 Salpa hexagona, Traustedt, loc. cit., p. .379, which see for further synonymy. 



Two specimens of the aggregated form of this species were collected in the North 

 Pacific on August 24, 1875, lat. 13° 1' 0" N., 151° 50' 0" W., from the surface, at night, 



