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I have nothing to add to Darwin's excellent description of this species, neither for the 

 hermaphrodite form nor for the complemental males. Darwin discovered that the latter were 

 attached in this species to the integument of the hermaphrodite, in a central line, between the 

 labrum and the adductor scutorum muscle, three individuals in a group. Opening the capitulum 

 of one of the "Siboga"' specimens I found the little males at once at the place indicated by 

 Darwix, the only difference being that I found not three but four of them attached to the 

 hermaphrodite. The size and form of the complemental male and of its rudimentary valves 

 (carina and scutum) are in the main as described by Darwix. The largest specimen measured 

 0,91 mm. (according to Darwix its length is =° ,000 of an inch = 0,89 mm.). The scutum is 

 narrow; it is considerably smaller than that in Darwin's figure, but it has exactly the size (0,2 mm.) 

 which it should have according to Darwix's description. The whole of the sac, which represents 

 a combination of capitulum and peduncle, is covered with very minute hairs. Beneath the 

 rudimentary carina and down the peduncular part of the sac are planted numerous much longer 

 spines which to a large e.xtent are bifid at the extremity. The fig. 13 of PI. V has been 

 drawn with the camera from the largest of the specimens. 



Darwin's specimens were from the Philippine Archipelago, Island of Bantayan, attached 

 to a horny coralline: 20 fathoms (about 36 m.). The "Siboga" collected it at the following places : 



Stat. 47. April 8 — 12, 1899. Bay of Bima (North Coast of Sumbawa). Depth 13 — 55 m. 



Numerous specimens. 

 Stat. 204. September 20, 1899. Lat. 4° 2o' S., Long. 122° 58' E. Depth 75—9401. Bottom: sand 



with dead shells. 2 specimens. 

 Stat. 213. Sept. 26 — Oct. 26, 1899. Saleyer anchorage and Surroundings. Depth down to 36 m. 



Bottom : coral reefs, mud and mud with sand. 6 specimens. 

 Stat. 294. January 23, 1900. Lat. 10° 12.2 S., Long. I24°27'.3E. Depth 73 m. Bottom: soft 



mud with very fine sand. 6 specimens. 



5. Scalpellum Peroni (Gray). PI. V, fig. 14, 14.-^, 14^. 



Smilium Peronii J. E. Gray, Annals of Philos. New series, X, 1825. 

 Scalpellum Peronii Darwin, Monograph. Lepadidae, 185 1, p. 264, pi. VI, fig. 6. 



I refer to this species the specimens of Scalpellum which were collected by the scientists 

 of the "Siboga" Expedition at the Jedan Islands. Most probably the place where they were 

 found is the anchorage off Palu Jedan, east coast of Aru Islands (Pearl Banks). 



There are in all three specimens, one of which is extremely small. The largest one has 

 been figured; it has a total length of 22 mm. and a capitulum of 13 mm. It is considerably 

 smaller than the specimens investigated by Darwix, which had a total length of little more 

 than one inch (25,4 mm.) and the capitulum of which measured about three quarters of an inch 

 (19 mm.). Perhaps the differences between the description and figure given by Darwix and the 

 specimens from Jedan must be ascribed to the circumstance that the latter specimens are not 

 quite full-grown. 



These differences are in the first place, that the spines which clothe the membrane 

 covering the valves and the interspaces are by no means so strong and so dense as they are 

 represented in the figure given by Darwix ; and secondly, that the rostrum and the subcarina, 



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