FAMILY GI.AUCID^E CAVOLINA. 11 



GENUS CAVOLINA. Brug. 



The general form and habits of the preceding, with retiform branchiae arranged in a series on 

 the dorsal surface on each side of the medial line. 



Cavolina salmonacea. 



PLATE VI. FIG. 116. 



C. salmonacea. Couthouv, Host. Jour. Nat. Hist. Vol. 2, p. G8, pi. 1, fig. 'J. 

 Eolis id. Gould, lnvertebrata of Mass. p. C. 



Description. Body nearly diaphanous. Back with a conspicuous elevation in the middle. 

 -Head large, with four tentacula ; the superior minutely serrated. Mouth an inverted ^ • 

 Branchiae in longitudinal series, to the number of one hundred or more. Foot with two short 

 processes in front, and ending in a point behind. Sexual appendages placed in a large tubercle 

 on the right side, a short distance behind the neck. Vent on the same side, near the centre 

 of the body. 



Color. Pale yellowish white. Branchial cirri salmon-colored, bordering on orange. 



Length, 1 ■ 7. 



GENUS FILURUS. 



Tentacula two. Gills in two series along the back. Vent terminal. Caudal appendage long 

 and filiform. 



FlLURUS DUBIUS. 



Description. Body cylindrical, enveloped in a loose transparent membrane through which 

 the intestinal tube is apparent. Along the back are two rows of branchial ? processes, six in 

 number on each side ; at their tips, furnished with five or six spiculae : these are only seen 

 when the animal is in motion. Mouth terminal, composed of a loose festooned membrane, 

 alternately dilating and contracting when the animal is in motion ; when dilated, two small 

 transparent tentacula are protruded. The abdomen, or upper surface, appears to be composed 

 of numerous rings. The caudal portion becomes abruptly smaller than the body, is long, 

 cylindrical, and tapering to a point. 



Color. Abdomen silvery white ; dorsal region and sides light brown ; tail light greenish. 

 The color of the body, however, appears to depend on the contained viscera. 



Length of body, 0"5; of tail, 0'7. 



This curious animal was taken while swimming in salt water with its body reversed. Its 

 motion was vermicular, and it appeared to be very tenacious of life, as it lived several days 

 in a vessel containing salt water which had not been renewed. 



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