58 NATURAL SCIENCE. July. 



characterised by their unsymmetrical shape, by the "extraordinary 

 unequal development of the two sides of the shell," as Darwin has 

 called it. Six new species of Verruca were added to the four previously 

 known. The shape of the deep-sea species of Verruca is very curious, 

 and I found it rather difficult to resist the temptation of introducing a 

 new genus in the system for their reception. Scalpelliun (PI. xiii., Fig. 3) 

 and Verruca are the only genera of Cirripedia observed at depths greater 

 than 1,000 fathoms. Dichelaspis ranges down to 1,000 fathoms; the 

 "Challenger" took a new species of this genus at this depth, the 

 depth at which the other species of this genus were taken being 

 unknown. The genus Balanus, of which forty-five species are known, 

 occurs from the shore down to 516 fathoms ; one of the five new species 

 of this genus collected by the " Challenger " was taken at that depth ; 

 another — the beautiful Balanus coroUiformis — was found to inhabit a 

 depth of 150 fathoms, the other four lived at less considerable depths. 

 Alepas and Poecilasma have each of them a new species in the 

 "Challenger" collection, living at 410 fathoms, and none of the 

 other known genera of Cirripedia (twenty-eight of the thirty-four 

 enumerated in 1883) was ever observed at a depth greater than 

 150 fathoms. In all, thirteen genera of Cirripedia are represented in 

 the " Challenger" collections, and most of them by highly character- 

 istic forms. For one of them, Megalasma striatum, the creation of a new 

 genus was necessary (PI. xiii.. Fig. 4). It is nearly related to Poecilasma, 

 but easily distinguished by the form of the scutum and the width of the 

 carina. Of floating forms of Cirripedia a dozen different species were 

 represented in the " Challenger " collections ; most of them were 

 well-known forms, but one of them was a new species of Chthamalus 

 taken from the screw of H.M.S. " Challenger," and so really deserving 

 the name of " Chthamalus challengeri." 



A supplementary report dealt with certain points in the anatomy 

 of the Cirripedia. The curious complemental males of the Cirripedia, 

 the segmental organs, the cement apparatus, Darwin's "true ovaria," 

 the eye of Lepas, and the female genital apparatus were treated 

 separately, as so many capita selecta of the morphology of these very 

 peculiar forms of animal life. 



P. P. C. HOEK. 



The grotesque and superficially spider-like creatures included 

 under Pycnogonida form, perhaps, one of the most compact and 

 homogeneous groups in the animal kingdom. Their true systematic 

 position, however, has never been accurately determined ; and 

 although some embryological evidence has lately been adduced in 

 favour of a possible but certainly remote connection between them 

 and the Arachnida, the difficulties in the way of establishing the exact 

 homology between the seven well-developed cephalothoracic appen- 

 dages of a pycnogon and the six of a spider or scorpion are so grave, 

 that the only course open to us is to follow Dr. Hoek in regarding the 



