CHELIDONURA. 35 



groove separates the posterior part of the body, which terminates 

 in two long filaments resembling the tail of a swallow. Mantle 

 [parapodial lobes] reflexed on each side, embracing head and body. 

 Color so dark that the eyes are not visible. The shell, contained in 

 the thickness of the mantle, is very small, thin, very open, slightly 

 spiral. Gill placed far back on the right side, forming the arc of a 

 circle, with its ramifications on the convex side. Ground-color very 

 deep blue ; top of the head, back, median line of posterior tails and 

 mantle-edge have a line of greenish-blue or emerald. One individ- 

 ual out of forty has a whitish cross on the back, and all the blue 

 lines are edged with a line of gold. 



Isle of France, (Mauritius) ; Fouquets, at low water. 



Sulla hirundinina Q. & G., Zool. de 1' Astro!, p. 367, pi. 26, f. 20- 

 25. B. (Chelidonura) hirundinina A. AD., in Thes., ii, p. 601, pi. 

 125, f. 167, 168. Chelidonura hirundinina MARTENS in Mobius' 

 Reise nach Mauritius, p. 305, pi. 21, f. 5, 6. Hirundella hirundina- 

 ria GRAY, Figs. Moll. Anim., p. 95. 



The specimens collected and drawn by Prof. Mobius are described 

 as follows (pi. 2, figs. 31-35) : 



When creeping 25 mill. long. Head with three low lobes, the 

 middle one lower than the others, behind prolonged in a tongue- 

 shaped lobe which lies over the back as far as the region of the 

 heart. The posterior segment of the body is higher and broader 

 than the head. It extends in two acute, laterally compressed ap- 

 pendages, which are outwardly convex, inwardly concave ; the left 

 appendage is larger than the right. The foot has lateral lobes 

 which extend up over the back to the median line or lap over a lit- 

 tle. One specimen (fig. 31) was brownish-black ; the head brownish- 

 red above, with an encircling red marginal line. On the back were 

 two long, brown tracts, bounded by red lines. The posterior body 

 also has a brown middle tract bounded by red, extending in two 

 points upon the terminal appendages, and two lateral tracts. Along 

 the red lines run blue-green lines. On the head there is a triangu- 

 lar yellow-white spot with fine black dots. A smaller lunate spot 

 of the same color is on the hind end of the tongue-like head-lobe, 

 and behind this a similar, larger spot on the back. Below and in 

 front of the latter the heart was seen to pulsate. 



A second specimen (fig. 32) was bluish-black with yellow spots, 

 more numerous on the back than on the ventral side; the reflexed 

 foot-margins on the back having a narrow clear green edge. 



