On some Helices /rom West Australia and the Mauritius. 29 



Labidocera Darwinii. 



There being as yet only one species in this family no specific 

 description need be given. 



Colour blue-green, sometimes with brown spots, y jjth inch in 

 length, 



Hab. Atlantic Ocean, lat. 38° south, in the open sea off the 

 coast of Patagonia. 



I received the specimens from Mr. Darwin, to whom I am 

 indebted for great kindness and advice, and who has kindly per- 

 mitted me to call it after him. 



EXPLANATION OF PLATE L 



Fiff. 1 . Labidocera Darwinii. Male. 



Fiff. 2. Second pair of antennae. 



Fiff. 3. Anterior antenna. 3 a. Prehensile apparatus open. 3 b. Ditto 



closed. 

 Fig. 4. Mandible. 

 Fiff. 5. First pair of maxillipeds. 

 Fi^. 6. Second ditto. 

 Fiff. 7. Third ditto. 



Fiff. 8. Thoracic leg : 1st, 2ud, Srd, and 4th pair. 

 Fiff. 9. Posterior thoracic legs. Male. 9 a. Left leg more magnified to 



show the penis. 9 b. Apical joint of penis. 

 Fiff. 10. Posterior thoracic legs. Female. 

 Fiff. 11. Abdomen. Female. 



IV. — Characters of several Helices from West Australia and the 

 Mauritius ; with Notes on some species of Cyelostoma from 

 Borneo. By W. H. Benson, Esq. 



1. Helix plectilis, nobis, n. s. }}f}i 



Testa subobtecte perforata, globulosa, albida, opaca, valde rugosa, 

 superne rugis perobliquis elevatis, angulato-flexuosis, irregnlaribus, 

 subtus versus umbilicum rectis, radiatis, munita ; spira elevati- 

 uscula, sutnris distinctis, apice obtuse ; anfractibus 4, convexis, 

 ultimo antice deflexo ; apertura circulari, perobliqua, peristomate 

 undique expanso, reflexinsculo, subcontinuo, margiuibus approxi- 

 matis, conniventibus, callo lato junctis, columellari late reflexo, 

 umbilicum plus minusve obtegente. 



Diam. major 15, minor 12, axis 10 mill. 



Hab. ad oras sinus " Shark's Bay " dicti Australiae Occidentalis. 



Remarkable for the bold, deeply fretted sculpture of the upper 

 side, extending below the periphery, and then merging into 

 moderate radiating folds. In form it wonderfully resembles 

 H. nivosa, Sow., of Porto Santo, but differs in the partly covered 

 umbilicus, the expansion and i-eflexion of the peristome, the cir- 



