i6y 



single row of hairs is situated parallel to the inner margin, between the denser tuft of hairs of 

 the extremity and the inner lobe. The inner lobe bears numerous long hairs on the semi-circular 

 innermost half; these hairs are distinctly feathered and are directed inwards and downwards. 

 The surface of the rest of the inner lobe shows numerous circular pits, looking like so many 

 places where hairs might have been disposed (PI. XIII, fig. 19). 



Cirri. First pair: rarni unequal, but not very strongly; the longer ramus has 17, the 

 shorter 1 3 segments. The shape of the segments may be seen in the figure. The six or seven 

 lower segments of the shorter ramus are distinctly protuberant on their inner face, the pigmen- 

 tation of the outer half of the segments extending over the protuberances (PI. XIV, fig. 1). 



Second pair has the rami slightly unequal, the longer with 14, the shorter with 

 13 segments; the whole cirrus is a little shorter than that of the first pair. The inner faces 

 of the segments of the longer ramus more protuberant than those of the shorter ramus. The 

 protuberances of the segments of the longer ramus are furnished with very conspicuous and 

 dense tufts of hairs (PI. XIV, fig. 2). 



Third pair has the rami also slightly unequal, of 13 and 12 segments respectively. The 

 rami are more robust, but hardly longer than those of the first pair. The inner faces of the 

 segments of the longer ramus are more protuberant than those of the other ramus. The tufts of 

 hairs disposed on the protuberances not so strongly developed as is the case on the second 

 cirrus. The projecting membranous plate fringed with fine bristles, which, according to Darwin, 

 is found on the thorax, on either side at the bases of third pair of cirri, was found well- 

 developed in the specimen investigated (PI. XIV, fig. 3 a). 



Fourth-sixth pairs equal in length and in number of segments. This number was 

 found to be 29 — and to vary between 28 and 30. The shape of the segments, in general, 

 is quadrate, the middle and lower segments being, however, broader than long, the outer 

 segments about as broad as long. The segments (PI. XIV, fig. 4) are slightly shield-shaped 

 in front, and bear only two pairs of longer spines : these are wanting on five or six of the 

 lower, and also on the last five segments of each ramus. Between the pairs of longer spines a 

 group of delicate hairs or spines is regularly observed. The hairs or bristles disposed on the 

 posterior side of the segments near the extremity are short. 



Penis. Relatively short, cylindrical, distinctly ringed, tapering towards the extremity. 

 Short hairs are scattered over its surface on the distal half, somewhat longer hairs being 

 disposed near its extremity. 



As I said already p. 164, the different forms or varieties of this species described here 

 were taken at the same time from the bottom of the "Siboga" when the ship was in the 

 doek, October 1899. As is well-known this species is common in all the warmer seas of the world. 



2. Sectio: Ortho-Balanus 



2. Balanus ampkitrite, Darwin. PI. XIV, fig. 8 — 17. 



Darwin, Ch., Monograph. Balanidae and Verrucidae. 1S54, p. 240, pi. 5, fig. 2a — 20. 



This species was collected by H. M. S. "Siboga" at half a dozen Stations and at depths 



39 



