i7 



but, of course, five other new species the descriptions of which have been published in 1900 

 by Gruvel \ two described by Lanchester 3 in 1902 and one by Annandale in 1906 3 , could 

 not fio-ure in his list. Thus 25 species in all of this genus are now known : in Gruvel's latest 

 publication* a synoptical table is given for the determination of these species. He even enumerates 

 (without Annandale's species of 1906) 25 species, as he also reckons to this genus a Lepadid 

 considered by Stebbing 5 to belong to another (and new) genus for which the name Trichelaspis 

 had been proposed by that carcinologist. 



The cruise of the Dutch gunboat "Siboga" has supplied us with several forms belonging 

 to this o-enus and I find that most of them must be considered as novae species. But before 

 entering on the description of these forms, I consider it useful to give a summary of the 

 descriptions of the known species in order to be able to judge of their relations and to under- 

 stand the difficulties of the classification. 



Aurivillius (1. c. p. 20 — 26) was the first who discovered a species of Dichelaspis, and 

 even five of them, without terga; in one of these species the carina is also wanting. I was at 

 first inclined to separate these species from the genus Dichelaspis. It would perhaps be more 

 in accordance with Darwin's original views, when only such forms were accepted as species of 

 this genus which had five valves and a scutum divided into two segments. This at least is the 

 original diagnosis of the genus. Stebbing therefore pointed out, that it would be difficult to 

 maintain the species of Aurivillius as species of the present genus. Yet looking at the question 

 again I finally embraced the opinion of Aurivillius in this matter. The structure of the body 

 of these problematic Dic/ie/aspis-species corresponds essentially with that of the typical, the 

 genuine, species of the genus, and in one of these species (D. cor) not only are the scuta 

 very typical Dic/ie/aspis-scuta, divided into two segments and with the primordial valves at 

 the rostral angle, but the capitulum has the position of the tergum distinctly indicated, as 

 it is limited by a chitinous cushion, towards the margin of the scutum as well as towards that 

 of the carina. Thus it would be extremely difficult and even unnatural not to consider that 

 species as a Dichelaspis, and once this is agreed upon, the other species are to be accepted 

 also, as they represent further stages in the degeneration of the valves of the capitulum in the 

 same direction as shown by D. cor, the last stage - - so far as known at present - - being 

 occupied by D. bullata Aurivillius, which species has no terga and no carina. 



Gruvel's new species D. Maindroni and D. Coutierei much resemble the form called 

 D. cor by Aurivillius and these belong by all means to the same section of the genus, which 

 section now counts seven species: five of Aurivillius and two of Gruvel. These seven species 

 most likely have another point of agreement, in that they are all living in a semi-parasitic way 

 in the branchial cavity or even attached to the branchiae of large brachyurous or macrurous 

 crustaceans. Four of the species of Aurivillius were even taken from the same Palinurns, not 

 species only but specimen, found stranded on the coast of one of the Thousand Islands, Java. 



1 Gruvel, A., Bulletin du Muséum d'histoire naturelle, 1900, n" 3, p. 109. 



2 Lanchestf.r, W., Crustacea of the Skeat Expedition. Proceed. Zool. Soc. London, II, 1902. 



3 Annandale, N., Stalked Bainacles in the Colombo Museum. Spolia Zeylanica, III, Part XI, 1906. 



4 Gruvel, A., Monographie etc. 1905, p. 140 — 141. 



5 STEBBING, T. R. R., A new Pedunculate Cirripede. Ann. & Mag. Nat. Hist. (6), XIII, 1S94, p. 443. 



17 

 SIBOGA-EXPEDITIE XXXI a. 



