1896.] or ITITS GENUS SEEGESTES. 951 



. To this group further belong *;S'. ham ife r, Ale. & And., which 

 I am not able to recognize, and the following larvae : S. inter- 

 medkis, Bate, S. diaponiius. Bate, S. ferinerhilcii. Bate, S. spini- 

 ventralis, Bate, and S. ventridentatiis, Bate, several of which 

 certainly belong to some of the species in the tabular view, but I 

 cannot recognize them ; S. macropJithalmus, Stimps., in all proba- 

 bility being a younger S. vigilax, Stimps. ; finally S. hracliyorrhos, 

 Kr., which is a very young larva of 8. edivardsii, Kr. (see later on). 

 S. aracJmipodus, de Nat., and S. profundus. Bate, I have not 

 been able to refer to any one oF the groups; to Petalidium ia 

 transferred S. ohesus, Kr. (S. sanr/uineus, Chun), and excluded as 

 not belonging to the genus are S. serrulatus, Kr., and S, cawdaius, 

 Kr. 



vi. Notes on the Species of Group I. 



A. a. S. tenuiremis, Kr. The specimen described by Kroyer 

 (p. 255, tab. iv. fig. 11, a-b) is a hardly half-grown Mastigopus; 

 S. longicolhis. Bate (p. 421, pi. Ixxvii. fig. 1), is almost (or perhaps 

 fully) adult ; S. jimceits, Bate (p. 416, pi. ixxvi. fig. 1), is the 

 young Mastigopus, 6 mm. long, with dorsal spines on the 4th- 

 6th abdominal segments. I have examined a specimen 23 mm. in 

 length, which had just obtained the black eyes ; the species grows 

 at least somewhat longer before maturity, but the mature form is 

 unknown. The obtaining of black eyes does not always take place 

 at the same length of the animal, as a specimen with the larger, 

 oblique, yellowish eyes is even 26 mm. long. The species is easily 

 separated from all other known forms by the combination of two 

 characters : the very long and slender body with the long distance 

 between the eye-stalks and the mouth-organs, and the ciliated 

 parts on the ext. br. of urp. occupying, in the older forms scarcely 

 ^, in the younger a little more than ^ of the exterior margin. The 

 quoted figure of ;S. longicollus. Bate (pi. Ixxvii.), gives a tolerably 

 correct notion of the species. 



It may further be added that of the two branchiae above trl.' the 

 first is long and the second a little more than half, the length of 

 the first and but a little shorter than the first branchia to trl.*, 

 while the second above trl.* is somewhat smaller, but still very well 

 developed. I have seen specimens of this species from numerous 

 localities in the Atlantic, northward to lat. 32° 16' N., in the 

 Indian Ocean, and in the Pacific as far as the Matelota Islands 

 and lat. 16° 8' S., long. 111° 50' E. 



A. 6. a. S. atlanticus, M.-Edw. As to the synonymy etc., sete 

 above. The best representation of this very common species is 

 given by Kroyer {S.frisii, Kr., p. 235, tab. i. fig. l,a-v). The 

 sixth joint of mxp.' consists of 6 subjoints, the 4 distal of equal 

 length and each of the 2 proximal as long as 2 of the distal 

 subjoints together. The branchial formula as in S.japoniciis, Bate 

 (S. mollis. Smith), viz. a podobranchia and a lamella to mxp.\ 

 a pleurobranchia and a lamella to mxp." and trl.'-trl.^, finally 2 

 pleurobranchisB to trl.^, but the branchiae are longer than in S. mollis. 

 Smith (Rep. Comm. Ksh and Fisheries f. 1885, pi. xx. fig. 5), and 



