On the Parasitic Copepod Thersitina gasterostoi. 415 



on the labrum, which is larger than the three others. The 

 denticles on the inner lip correspond to the terminations of 

 spirals around the lower part of the whorl. The notch on 

 the inner edge of the columella is smooth and situated oppo- 

 site the second denticle from the anterior end. 



CaUiostoma roseopictum. (PI. IX. fig. 4.) 



Testa parva, conica, anguste umbilicata, raaculis roseis et albis picta, 

 supcrne virescens efc pallide cornea, ad basini lineis tribus con- 

 centricis roseis aliisque radiantibus ornata ; anfractus sex, 

 superiores tres convexiusculi, keves, dilute carnei, duo sequcntes 

 plani, subvirides, roseo plus minus picti, ultiruus ad peripheriam 

 rotunde angulatus, roseo alboque articulatus ; ultimus et penulti- 

 mus spiraliter regulariter striata, striis vel sulcis sex angustis- 

 siruis, quam interstitiis longe angustioribus ; basis infra angulum 

 convexiuscula, versus urubilicum augustum album magis tenuiter 

 eoncentrice striata ; columella oblique arcuata ; labrum intus 

 incrassatum, album ; apertura intus margaritacea, obsolete 

 sulcata. 



Alt. 4*3, diam. 3 mm. 



The specimen here described, although very small, appears 

 to be adult, since the outer lip is thickened within. The 

 thread-like sulci upon the spire and the three upon the base 

 are coloured, and contrast clearly with the ground-colour of 

 the shell. The former are brownish and the latter more 

 rosaceous. 



The spotted lira at the periphery passes up the spire, 

 forming a distinct margination beneath the suture. 



This species is evidently closely allied to C. marmoreum, 

 Pease, from the Paumotus, and may eventually prove to be a 

 small, less elongate, and differently coloured variety of it. 



EXPLANATION OF PLATE IX. 



Fir/. 1. Engina fuscolineata, sp. n. 



Fig. 2. Tritonidea difficilis, sp. n. 



Fig. -j. rosacea, sp. n. 



Fig. 4. CaUiostoma roseopictum, sp. n. 



L. — Some Notes on the Parasitic Copepod Thersitina 

 gasterostei, Pa gen steelier. By Robert Gurney, M.A. 



[Plates X.-XIII.] 



The family Ergasilidsc, to which Thersitina belongs, lias 



recently been most ably monographed by Wilson *, so far, 



* C. B. Wilson, Froc. U.S. Nat. Mus. xxxix. 1911, pp. 263-400. 



