184 PERCY SLADEN TRUST EXPEDITION 



tion*. The body is cylindrical, enveloped in a thin, but inflated cutis, forming at the 

 throat at either side a fold, such as generally occurs in Pterotrachea. On the fold some 

 minute spinules are to be found, the only structure of the kind in this species, as I 

 observed none elsewhere, neither on the body, nor before the eyes. The proboscis is 

 stout, measuring £ of the total length. Fin large, rounded ; sucker conspicuous. Visceral 

 nucleus inflated, short, bearing about nine gills at its proximal and left side. Tail high, 

 owing to accidental contraction ; the muscular bands and the horizontal fins do not exhibit 

 any characters worth mention except for a row of spines on the third muscular band. In 

 the region of the fin the characteristic circular glandular organs of Pterotrachea are 

 scattered about ; on the anterior part of the body and on the proboscis occur numerous 

 pale spots, likewise of a glandular nature, and similar to those occurring in the 

 Carinariidae. 



The eyes of this species have the characteristic shape on account of which I founded f 

 the subgenus Euryops. They are figured very accurately by Hesse \. 



One of the specimens of this species in the Siboga material exhibited a few indistinct 

 purpureous spots on the body. For tins reason, and because of the lack of spines before 

 the eyes, I think it not improbable that my species is identical with Pt. mutica Gegenbaur, 

 Keferstein, Cams, nee Lesueur, Vayssiere. The great confusion however in the nomen- 

 clature, especially of the Pterotracheidae, does not warrant any certainty about the truth 

 of my surmise, and a renewed and thorough review of this group of animals, notably from 

 the Mediterranean, would be a valuable task for any naturalist. 



Firoloida Lesueur. 



19. Firoloida koivalewskyi Vayssiere. 



Stat. A (2), N (1), Chagos Archipelago; a (6), c (2), Mauritius; x (2), Providence; 

 aa (2), bb (1), N. of Providence ; dd (12), ee (l), kk (3), 11 (l), mm (2), Amirante Group. 



This species was found at 12 stations, especially from the Amirante Group, with 

 a total number of 36 specimens. It is remarkable for its distinct sexual dimorphism, 

 pronounced (1) in the presence or absence of a sucker and of tentacles, (2) in the different 

 form of the tail, (3) in the unequal development of the vei'y small gills. To my former 

 statements§ I can add that I found this last character somewhat modified, as in some 

 female specimens the gills are very inconspicuous, or even altogether wanting. 



I am much inclined to suppose all the so-called different species of Firoloida described 

 by various authors will prove to be the same species, identical with F. koivalewskyi. All 

 Firoloida specimens I have examined exhibited essentially the same features. Even 

 F. desmaresti, as figured recently by Vayssiere ||, notwithstanding the accurate descrip- 

 tion, does not differ in the main from the species now recorded from the Sealark. The 

 male of F. kowalewskyi agrees in all respects with that of F. desmaresti, judging frum 

 Vayssiere's account, except for the caudal filament, which is not always provided with 



* I.e. p. 88, PL xm. figs. 86—89. + I.e. pp. 83, 84. 



% Die Augen einiger Mollusken, Zeitschr. iviss. Zool. Bd. lxviii. 1900, PI. xxix. figs. 57, 58. 



§ I.e. pp. 90—95, PL xiv. 



|| I.e. pp. 43—45, PL IV. figs. 66—68, PL v. figs. 69, 70, 76. 



