Oyi the Genera of the Dromiidas. 297 



XXXIX. — Description of a tiew Species 0/ Balanus /rom the 

 Collection of the British Museum. By Prof. A. Gruvel. 



Balanus violaceus, sp. n. 



Diagnosis. — Walls and base porous. Radii well deve- 

 loped, not pierced by pores. Test violaceous in general 

 colour, with numerous narrow, longitudinal, clear grey-blue 

 ribs. Base entirely porous. Scuta with the articular 

 ridge very prominent, the ridge of the adductor feebly 

 developed and situated a little nearer the rostral than the 

 tergal margin ; pit for the adductor muscle deep ; cavity 

 for the lateral depressor muscle also deep. Terga with the 

 lidge and the articular furrow very clearly marked ; spur 

 prominent at the rounded lower extremity, and situated 

 at a slightly less distance than its own width from the basi- 

 scutal angle ; crests for the depressor muscle very distinct 

 and prominent; no external longitudinal furrow, but, on the 

 contrary, a longitudinal ridge ; apex slightly projecting, 

 terminating in a blunt point. 



Habitat. Unknown. 



N.B. — This species comes near to B. nuhilus, Darwin, and 

 consequently its place is in section C. 



XL. — On the Genera of the Dromiidte. By L. A. BORRADAILE, 

 M.A., Lecturer in Natural Sciences at Sehvyn College, 

 Cambridge. 



Since Bouvier's paper " Sur I'Origine homarienne des Crabes " 

 (Bull. Soc. Philom. 1896) the limits of the genera of this 

 family of primitive crabs have become very uncertain. In 

 the list of genera and species of the Dromiacea which he has 

 lately published* Alcock has included Slimpson's Dromidia^ 

 with Dromia as a subgenus, and placed Dromidiopsis '\ with 

 Dromidia as synonymous, regarding Cryptodromia, Stimps., 

 as still an independent genus. In working out the collection 

 of Dromiidyj made by the late Maldive Expedition I have 

 been led to conclusions which differ from these with regard 

 to the genera Dromidia and Dromidiopsis and support 

 the view hitherto held of their generic distinctness. More- 

 over^ it has seemed that certain other rearrangements are 



* ' Catalogue of the Indian Decapod Crustacea iu the Collection of the 

 Indian Museum,' part i. fascic. 1, pp. 74-80 (1901). 

 t Borradaile, P. Z. S. 1900, p. 572. 



