so different, that I would hardly have taken the animal for an abnormal P. diibium^ if I had 

 received it from a quite different Station. Comparing the different valves with those of a normal 

 P. dtibium, the tergum in the first place is larger, its apex is slightly recurved and its basal 

 angle is not truncated but rounded. In the second place, the scutum is broader and its tergal 

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

 regularly bowed, but its upper part is recurved, and there is further a small isolated piece of 

 valve, which I think belongs to the carina, and which is placed between the tip of the remaining 

 part of that valve and the inferior angle of the tergum. In this specimen, moreover, the peduncle 

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

 The total length of this specimen was 7,2 mm., that of its capitulum about 5 mm. 



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

 an abormal way. They were most probably dead, when they were 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 D.\rwix 

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

 exact shape of the valves, more especially of the terga (I.e. 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 

 abnormalit\' in the process of calcification or shell-building. Under P . excavahtin I describe another 

 case of such abnormality — without trying to explain its origin. This will be the task of future 

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



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



Poecilasuia jissa Darwin. Monograph, Lepadidae, 185 1, p. 109, pi. II, fig. 4. 



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

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



Numerous specimens were taken from a Palimiriis, collected at Ternate during the cruise 

 of H. M. S. "Siboga". There are about six larger 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 

 \alves etc. applies so well to the specimens from Ternate that there remained for me no doubt 

 as to these specimens really belonging to Darwin's Poecilasuia Jissa. There are little differences, 

 however, 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 been kept dry" and little difterences 

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

 not caused what I suppose to be the same species to be described by Aurivillius as a new 

 one under the name of P . aviygdalitm \ For this reason especially, the following details of 

 the animals structure may be of interest. 



Aurivillius, C. W., Studien itber Cinipedien. K. Svensk. Vetensk.-Akad. Handl. XXVI, X" 7, 1S94, p. 10. 



