521 



Two NEW Bdelloida commensal in the branchial cayities of 



Tl^LPHVSA FLUVIATILIS, LmK. 



By Sebastiano Piovanelli. 

 {Read June IdtJi, 1903.) 



While examining the branchial cavities of the common 

 Italian fresh-water crab, Telj^husa Jiuviatilis, I found two forms 

 of Bdelloid Rotifera commensal therein and not referable to 

 described species, one having distinctive characters of such 

 importance that I propose to place it in a new genus. 



Mr. Bryce has very generously aided me with valuable 

 information and adv^ice in compiling the following descriptions. 

 The observations on which these descriptions are based have 

 been made in Professor Decio Vinciguerra's laboratory in the 

 K. Stazione di Piscicoltura, Museo Agrario, Home, and under 

 his guidance and supervision. 



Callidina cancrophila, n. sp. 



Slender and parallel-sided, 426— 530 /x in length. Skin smooth, 

 wdth dorsal and lateral longitudinal folds. Colour greenish grey. 

 Width of corona, 67/i., scarcely more than collar; of neck, 53/x. 

 Kami formula, 2/2 ; length, 27 /a; maximum width of each ramus, 

 11 /x. Antenna rather flattened antero-posteriorly, about 16/x 

 long. On the first cervical, at each side of the antenna, a small 

 boss of thickened hypodermis, which extends down each side of 

 the segment in a slight and decreasing ridge. A rather promi- 

 nently angular lateral outline is presented by the anal segment. 

 The first foot segment, though smaller, presents, from dorsal or 

 ventral view, a similar appearance, but the angularity is due 

 to a deep thickening of the hypodermis, w^hich increases to a boss 

 dorsally. Foot of four joints, 93 yu, long. Spurs stout and strong, 

 pointed, with distinct heel ; outside edge boldly convex, slightly 

 angular at about one-third from tip ; inner edge below heel 

 nearly straight or slightly concave. They are somewhat rigidly 

 attached and their pose is characteristic, as they are widely 

 divergent, and rather erect relatively to the foot axis. Length, 

 25/x; interstice, 4/x, convex. Toes three, rather stout. 



Commensal in the branchial cavities of Telphusa fiiwiatilis, 

 Lmk. 



