REPORT ON THE CIRRIPEDIA. 23 



This list may be condensed into the following table, showing approximately how 

 many times Cirripedia were dredged at certain depths. 

 Twelve species were taken at the surface. 1 



From dredgings in depths of from to 500 fathoms 21 times. 



As the exploration of the coasts of islands and continents was of secondary importance 

 during the cruise of H.M.S. Challenger, we need not wonder that the Cirripedia of 

 these regions are badly represented in the collections made during the voyage. Only 

 occasionally were specimens collected in the neighbourhood of the coasts. At the same 

 time this explains how it is that only a small percentage of the specimens collected 

 belong to species described before : out of seventy-eight forms represented in the 

 collection, nineteen only have been previously described, and fifty-nine are named and 

 described here for the first time. 



In 1854, Darwin 2 said "the number of known existing Cirripeds is 147." Since 

 that date this number has only slightly increased. I am only aware of eighteen 

 new species, but, as I have already said above, I am far from certain that I have 

 brought together all the information which might be had from zoological literature. 

 There can be little doubt, however, that this number is inconsiderable in comparison with 

 the number Darwin knew when composing his Monograph, and also in comparison 

 with that added during the cruise of H.M.S. Challenger. Hence I thought it would 

 be of bttle use to prepare a list of all the species known at present, as I did in my Bejsort 

 on the Pycnogonida, in imitation of what Mr. Davidson had done for the Brachiopoda. 

 I merely insert in the following table a list of the genera at present known, giving 

 in separate columns the number of species known to Mr. Darwin, described since 

 the publication of his Monograph, and collected during the cruise of H.M.S. 

 Challenger. One of the columns gives in fathoms the hitherto ascertained depth of 

 each genus. 



We learn from this list that out of thirty-four genera of Cirripedia at present known, 

 twenty-eight have never been observed at a depth greater than 150 fathoms. Two have been 

 found from the shore to 400 fathoms {Alepas and Pcecilasma) ; Balanus occurs from the 

 shore down to 510 fathoms ; Dichelaspis ranges down to 1000 fathoms, and finally, only 



1 Some of them in numerous places — as, for instance, Lepas anatifera — others only once ; so Balanus tiaHnnabwlum, 

 var. spinosus, taken from the screw of H.M.S. Challenger at St. Vincent. 



2 Loc. tit., p. 166. 



