NEMATOMENIA-ICHTHYOMENIA. 305 



the cuticle, on which they rest only by the bases ; but these spicules 

 are narrower, lanceolate (fig. 81, below), always notched at the base, 

 with some sparsely scattered among them (fig. 81, above) of a club- 

 shape ; there are also all transition forms between these. The tail 

 end (fig. 80) instead of being slightly narrowed as in M. banyulensis, 

 is transversely truncated ventrally, prolonged dorsally in a short 

 finger-shaped appendage. The sensitive organ, situated on the 

 median dorsal ridge some distance from the lower end of the body 

 {fig. 82) consists of a small hyaline prominence bristling with a 

 great number of extremely fine tactile bristles, and encircled by a 

 crown of very small lanceolate spicules. Length 40 mill., width 1 

 mill. 



On Lafoea dumosa, at Banyuls, in 45-90 meters. 



Dondersia flavens PRUVOT, Arch. Zool. Exper. (2), ix, p. 718, 

 781 ; pi. 25, f. 2; pi. 31, f. 81. Nematomenia flavens SIMROTH in 

 Bronn, p. 232, pi. 6, f. 5-1 1 . 



Genus ICHTHYOMENIA Pilsbry, 1898, n. n. 



Ismenia PRUVOT, Arch. Zool. Exper. (2), ix, p. 719, 784, 1891. 

 Not Ismenia King, 1850 (Brachiopoda) nor Ismenia Desv., 1863 

 (Diptera). 



Body cylindrical-conic, broader behind, narrowed in front. 

 Cloaca opening a terminal transverse slit, a prominence in front of 

 it. Foot-groove and foot present, disappearing posteriorly. Cuticle 

 not papillose, the ventral spicules leaf-shaped, the rest scale-like, 

 imbricating. No gills. Radula well developed, apparently with 

 two rows of teeth. Length 5 to 6 times the breadth. 



I. ICHTHYODES (Pruvot). PI. 46, figs. 69-73. 



Body pale yellowish roseate, 12 mill, long, without a keel, but 

 with a median dorsal line formed by the convergent spicules ; pedal 

 groove large (fig. 70) ; cuticle smooth, with leaf-shaped spicules (fig. 

 71) near the ventral sulcus, 0*06 mill, long and a third that 

 breadth, outside of which is a wide band of strong spicules shaped 

 like a paper-knife, O'l mill, long, covering and protecting the 

 former; then follow spicules (fig. 73) of nearly the same form but 

 smaller and striated ; the rest of the surface with smaller discoidal 

 spicules (fig. 72), which are very thin, with pectinated edge and a 

 smooth, thick semicircular ridge. Their form and imbrication re- 

 call the ctenoid scales of fishes. The conspicuous peculiarity of the 



