32 THE VOYAGE OF H.M.S. CHALLENGER. 



carinata, presenting several very striking points of difference (PI. XXIII. fig. 2 ; PL 

 XXXIII. figs. 1,2; PI. XXXIV.). They fall into several sets, each of which represents 

 a different type of Comat u/a-structure, and in several cases the distribution of these 

 sets is fairly well defined. 



The ten-armed species of Antedon have a wider range both in depth and in space than 

 any other types of the genus. This is of course only to be expected ; for they represent 

 a somewhat early stage in the development of the Pentacrinoid larva, the radial axillaries 

 and the pairs of first brachials which they bear appearing soon after the opening of 

 the tentacular vestibule, when the whole number of tentacles does not exceed twenty- 

 five. 



These ten-armed forms are the only species of Antedon which occur outside the 

 fortieth parallels of latitude, and at greater depths than 750 fathoms. There is one 

 possible exception to this last statement. Some examples of Antedon insequalis with 

 three distichals reached me, together with fragments of Pentacrinus naresianus and the 

 label of Station 175 (1350 fathoms). But there is no record in the Station Book of their 

 occurrence here, though two Comatulae are mentioned. But these [Antedon breviradia and 

 Antedon acutiradia, PI. XI. figs. 3, 5) have the general facies of deep-water forms ; and this 

 is not the case with Antedon insequalis and the arms of Antedon basicurva, which are 

 labelled as coming from this station. It may then, I think, be safely assumed that the only 

 Cornatulae dredged at Station 175 were the ten-armed Antedon acutiradia and Antedon 

 breviradia, the multibrachiate Antedon insequalis not really occurring at that station. 

 Disregarding this form, we find that out of twenty-nine stations where Antedon was 

 dredged by the Challenger, "Porcupine," and other British expeditions, at depths exceeding 

 200 fathoms, twenty-eight yielded ten-armed species. Multibrachiate species occurred at 

 six of these, and at one other station, this (Station 135g) being the only locality below 

 200 fathoms where the genus Antedon occurred, but was not represented by any ten-armed 

 form. Eleven of the twelve " Porcupine " stations ' and two of the seventeen Challenger 

 ones were beyond the parallels of 40°. But the remaining " Porcupine " station and six 

 of the fifteen Challenger ones within these limits yielded multibrachiate forms, though 

 never at a greater depth than 750 fathoms. The " Porcupine " species, however, Antedon 

 lusitanica, is a curious one. It is dimorphic, some individuals having ten arms only, 

 and some having one or more distichal series (PI. XXXIX. figs. 1, 3). 



The nine dredgings of the Challenger at which Antedon occurred at depths between 

 700 and 2900 fathoms inclusive, yielded nine species of the genus, all of them small and 

 ten-armed, and half of them belonging to the group which contains the familiar Antedon 

 rosacea and Antedon tenella. Four of the fifteen dredgings between the fortieth parallels 

 at depths exceeding 200 fathoms were at 1000 fathoms and upwards, and they yielded 



1 Under this general name I include all the dredgings of the " Porcupine," " Lightning," " Knight-Errant," and 

 "Triton." 



