whole cirrus only little longer than the 2 nd and having 9 and 10 segments in the two rami. 



Fourth pair has 16 to 18, fifth 18 to 19, 6 th pair 19 to 20 segments. All the segments 

 (with the exception of the two or three last ones, which have only two pairs of spines) are 

 furnished on their inner face with three pairs of spines (PI. XXII, fig. 25) of unequal size. 

 Each segment has at the outer face near the extremity a tuft of spines, of which one is longer, 

 its length nearly equalling that of the segment. The shield-like swellings at the base of the 

 3 ld to 5 Ul cirri are furnished with dense tufts of long hairs which are directed towards the 

 hindermost part of the body. 



Penis is rather short ; hairs on distal part directed perpendicularly to the long axis, 

 a rather dense tuft is situated at and round the extremity. 



The specimen was furnished with eggs in the mantle-cavity. The eggs have an elongately 

 oval shape, are not quite twice as long as broad or thick ; their long diameter is about o. 1 7 mm. 



The specimen was collected at : 



Stat. 164. August 20, 1899. Lat. i°42.5S., Long. i30°47.5E. Depth 32 m. Bottom: sand, 

 small stones and shells. Several other species of Balanus (see the list in the 

 introductory part) were collected at this Station. 



Geographical Distribution. According to Darwin this species is found on the 

 West Coast of Africa, at Tubicoreen, near Madras and in the Mediterranean (?). According to 

 Weltner (Verzeichniss, 1897), the Berlin Museum has specimens from Japan, from West-Australia 

 (Mermaid Strait), and from Guinea. All the Berlin specimens are attached to Gorgonidae. It 

 therefore seems to have a world-wide distribution, and we cannot be astonished that it was 

 found also in the Malay Archipelago. 



The depth at which it was collected on former occasions is not mentioned. 



22. Balanus navicula Darwin. PI. XXII, fig. 26. PI. XXIII, fig. 1 — 3. 



Darwin, Ch., Monograph. The Balanidae, Verrucidae etc. 1854. p. 221, pi. III, fig. 6a — 6d. 



A very small Balanus attached to a small stem of a Gorgouia, looks much like the 

 figure of the above-named species (PI. XXII, fig. 26, a and 5) given by Darwin. The nar- 

 rowness of the carino-lateral compartments and an indication of striae on the surface of the 

 scutum decided me to consider the specimen as belonging to this species. 



The longest basal diameter, which according to Darwin is 0.4 of an inch — over 10 mm. - 

 in the Siboga-specimen measures only 2.6 mm.: it is, probably, a very young specimen. The 

 rostrum is elongate, but the basis does not enclose the branch of the Gorgonia, therefore it 

 is not furrowed as the case is in B. calceolus. 



The scutum (PI. XXIII, fig. 1, a and c) corresponds well with Darwin's description, 

 but the raised striae which should radiate from the apex in my specimen are indicated only by 

 lines not very distinct. The adductor ridge is not developed, the articular ridge elongated. 

 The tergum (PI. XXIII, fig. 1, b and d) is slightly beaked, its scutal margin is nearly straight, 

 whereas in Darwin's figure it is somewhat hollowed out. The tergum is extremely brittle and 

 its spur was broken off in'both valves, therefore I am not quite sure that the figure given is 

 quite exact. 



95 



