tli.tt I wou ld hardly have taken the anima] for an abnormal /'. t////>i//w, if I had 

 ,i quite different Station. Comparing the different valves with tho a normal 



rgum in the first pla< trger, its apex is slighdy recurved and its I 



not truncated but rounded. In the second place, the scutum is broader and il 

 much longer than in the typical specimens. Finally, the carina is not simply and 

 irl) bowed, but its upper part is recurved, and there is further a small isolated pi» 

 . which I think belongs to the carina, and which is placed between 1 1 1 « - tip of the remaining 

 part ol th.it valve and the inferior angle of the tergum. In tliis specimen, moreover, the peduncle 

 is longer than in the other specimens, its length being about . of the length of the capitulum. 

 The tut. il length of tliis specimen was 7,2 mm., that of its capitulum aboul 5 mm. 



I do not know what circumstances or causes made these four specimens develop in such 

 an abormal way. They were most probabl) dead, when they wefe taken by the "Siboga". I 

 conclude this in the first place from the fact that the animals were hanging out of the capitulum 

 in a more or less deteriorated condition, in the second place from the circumstance that 

 numerous stalked Infusoriae are attached to the surface of the capitulum in all. As Darwin 

 ierved more than half a century ago, there is often very considerable variation in the 

 exact shape of the valves, more especially of the terga (l.c. p. 29 . In the present instance it is, 

 however, not so much variation in shape as that in three of the four specimens, at least, there is 

 abnormality in the process of calcification or shell-building. Under P.excavatum I describe another 

 ■ >t' such abnormality without trying to explain its origin. This wil] be the task of future 

 investigators who study these animals in the fresh condition and at the place where they occür. 



4. Poecilasma fissum Darwin. PI. X, fig. 2 — 5. 



Poecilasma fissa Darwin. Monograph, Lepadidae, 1851, p. ioy, pi. II. fig. 4. 



Darwin founded this species for a single specimen of Poecilasma which he took from a 



spinose crab found under a stone at low water in the Island of Bohol, Philippine Archipelago. 



Numerous specimens wen- taken from a Palinurvs, collected at rernate during the cruise 



of II. MS. "Siboga". There are about six Iarger and about fifty smaller specimens. The larger 



ones measure about 8 mm., 4,5 to 5 mm. coming on the capitulum, 3,5 to 3 on the peduncle. 



Darwin says that the capitulum of his specimen was nearly a quarter of an inch long 



and that its shape was gibbous, broadly oval. The description he gives of the capitulum, the 



valves etc. applies so wel! to the specimens from Ternate that there remained tor me no doubt 



.i> to these specimens really belonging to Darwin's Poecilasma fissa. There are liule differences, 



ver, in the structure of the parts of the mouth, the cirri etc. Darwin's description was 



founded on a single specimen which moreover "had long heen kept dry" and little differences 



occur within the limits of a species. I would hardly insist on these differences, had they 



■d what I suppose to 1»- the same species to 1m- described by Aürivillius as a new 



name of /'. amygdalum^. for this reason especially, the following details of 



ructure ma\ he of interest. 



- dien b« u. K. Svensk. Vetensk H Ddl. XXVI, N" 7. 1894, p. 10. 



8 



