189G.] OF TJIE GENUS SEllOESTES. 963 



third segment is longei* than the iirst or the second hy one-half." 

 Unfortunately Faxon does not describe or figure the sixth joint 

 of mxp.' I think that the species will prove to be different 

 from S. incertus, iii. When Faxon states that 6 large pleuro- 

 branchise and one smaller podobranchia are present on each side 

 on the body, he cerlaiiily has overlooked the 6 lamellse, which I 

 have found in ;S^. incerius and the other species of the edwardsi- 

 group. 



S. Iiamifer, Ale. & And., I will mention here, though I have 

 not been able to insert it in my tabular view. The description 

 (1894) and the figure (1895) plainly show that it belongs to this 

 group. As in mxp.' " the propus is four-jointed," the species cannot 

 be identical with S. edwardsi, Kr., but it is impossible for me to 

 settle whether it be really valid or synonymous with one of the 

 other species. Only two characters 1 have been able to detect, 

 viz. : that mxp.' seems to be still longer than in any other species, 

 and that its fitth joint is curiously arcuated (see the figure); but it 

 is difFicult to say whether these two characters are valid, for 

 instance, to decide whether the shape of the mentioned fifth joint 

 may not be due to some artificial cause. The species must be re- 

 examined. 



As mentioned above, I have examined five older Mastigopus- 

 forms, four of which have been elsewhere described. The older 

 specimens, c. 10-15 mm. in length, are easily recognized from 

 each other, and some few characters shall be pointed out ; but the 

 younger stages are mofe dilficujt, being more spiny, &c., aud 

 besides the materials seen by me are rather insufficient, and the 

 animals difficult to characterize without the aid of figures. The 

 larvae are easily distinguished from all larva) in Group I. by the 

 elongated and vigorous mxp.'', and from S. sargassi, Ortm., by the 

 longer eye-stalks. In the old larvte the sixth joint of mxp." is 

 divided into 4 subjoints (the oldest larval stage of S. oeulatus, Kr., 

 is unknown to me, so that I cannot settle whether its two distal 

 subjoints are divided as in S. edwardsi, ICr.), but the armature 

 on the end and on the interior margin is very different from that 

 in the adults. 



S. oeulatus, Kr. — Kroyer has given a good representation (p. 243, 

 tab. iii. figs. 5, a-f) ; Bate has also described and figured it (p. 406, 

 pi. Ixxiv. fig. 1 ). Both Kroyer and Bate figure, in my opinion, 

 the eye-stalks a little too long. The rostrum is short, seen from 

 the side obliquely triangular, acute, and rather broad at the base ; 

 the abdominal segments are dorsally smooth — even in a specimen 

 but 6'5 mm. long — and on the ext. br. of urp. the exterior margin 

 is ciliated in the total or almost the total length (in a larva 10 mm. 

 long, c. -j-^, measured with .accuracy, of the length was naked). 

 By the combination of these three characters the older specimens 

 are easily recognized. The species is most decidedly the Mnsti- 

 gopus of S. edwardsi, K.T.—S. hruchyorrhos, K.T. (p. 272, tab. v. 

 figs. 13, a-h), is the young Mastigopus of S. edwardsi, Kr. I have 

 examined Kroyer's type specimen, which is about 4 mm. long. 



