64 
THE VOYAGE OF H.M.S. CHALLENGER. 
Genus 5. Caudina, Stimpson, 1853, von Marenzeller, 1881. 
Eetractor muscles absent. Calcareous ring with five bipartite posterior prolonga- 
tions, Tentacles twelve to fifteen, digitate (or terminating in a disk ?). Caudal 
portion very long and narrow. Deposits — circular perforated disks or cups. 
Caudina arenata {Chirodota), Gould, 1841; Pourtales, 1851; Stimpson, 1853; Ayres, 
1854 ; Selenka, 1867 ; Semper, 1868 ; von Marenzeller, 1881 ; Kingsley, 1881. 
Tentacles fifteen, each with about four digits. Deposits — rounded circular disks with 
slightly undulating margin, and perforated with eight to twelve holes arranged 
round a central opening which often seems to he quadrifid. 
Habitat. — Chelsea Beach near Boston (Gould, Pourtalfes, Verrill, &e.), Massachusetts 
Bay (Verrill, Stimpson), Vineyard Sound to Chelsea (Verrill), Grand Manan 
(Ludwig, Selenka), Eevere Beach, Mass. (Kingsley). 
The accounts of the tentacles in this species are various, Gould only found eleven ; 
Selenka and Ayres assert them to be twelve ; Pourtales has observed their 
number to be fifteen, each divided into five lobes ; and, finally, von Marenzeller 
who has had the opportunity of examining numerous specimens, states them to 
he fifteen, each with four digits, of Which two at the top are minute. 
Caudina ransonnetii, von Marenzeller, 1881 ; Ludwig, 1883. 
Tentacles fifteen, like those in the preceding species. Deposits — regularly perforated 
very flat cups with outwardly, upwardly directed teeth in the margin ; the opening 
of the cups is closed by an x -shaped figure with low-knobs in the centre and at 
the ends of the arms. 
Habitat. — Yellow Sea (von Marenzeller), Japan (Ludwig). 
Caudina coriacea [Molpadia], Hutton, 1872 and 1879. Echinosoma (?) coriacea, 
Hutton, 1879. Caudina oneridionalis, Bell, 1883. 
Habitat. — Wellington, New Zealand (Hutton, Bell). 
The description of Hutton is too summary to communicate an idea of the animal in 
question. However, in the State Museum of Stockholm I have seen two 
specimens dredged at Wellington and presented by Hutton under the name of 
Molpadia coriacea. Hence I am able to state the correctness of the synonymy, and, 
though I could not examine the tentacles, I venture the suggestion that Hutton’s 
species is identical with, or, at least, very nearly allied to, the above species of 
von Marenzeller. The absence of true retractors, the long tad, and, above all, 
the characteristic deposits, speaks for this close relation. However, there may 
exist some small differences in the shape of the calcareous ring, the bifurcate 
prolongations of the radial pieces being slightly longer and more slender in the 
