2-12 MR. S. HANLEY ON A NEW LEDA. [June 11, 



Only two specimens of this Crab have fallen in my way. One ia 

 in the British Museum, and the other is in my own collection at 

 Madeira. To both were attached numbers of the rare cirripede 

 Pcecilasma crassiim, Darwin. I have named it in honour of that 

 learned carcinologist, the President of the Linnaean Society, and the 

 author of a memoir on the genus Cancer, printed amongst the Trans- 

 actions of that body. 



5. Description of a New Leda. By Sylvanus Hanley. 



Leda dohrni. Testa ohlongo-acufa, vix incequilateralis, con- 

 vexa, cute paUide straminea mduta, antice siiblcBvigata, postice 

 et in medio costata ; costis plamdatis ; interstitiis ang^istis, 

 Icevibus. Extremitas antica anguste rotundata : latus posticum 

 gradatim acutangidare. Plicce umbonalis situs ordinarius an- 

 gulatim et repente depressus. Margo dorsaTis utrinque modice 

 declivis, antice convexus, postice subrectus ; ventralis subar- 

 cuatus, utrinque {sed antice prcesertim) acclivis. Area dorsalis 

 antica vix impressa, suhconcentrice sulcata ; postica satis magna, 

 impressa, subconcentrice costellata. Nates acutce, vix elevatee. 

 Umbones IcBvigati. 

 Hab. Mare Pacificum. 

 Mus. Dohrn. 



The anterior side, which, if either, is the shorter, is smooth, or, at 

 most, obsoletely grooved, and is marked with a radiating shallow in- 

 dentation, that is chiefly perceptible near the ventral edge. The sur- 

 face is rather glossy : the ribs become subimbricated near the hinder 

 dorsal area. The posterior dorsal slope is straightish, or subretuse 

 (except in the middle) : the hinge-margiu is broad ; and the teeth 

 numerous on both sides of the small cartilage-pit. 



6. Descriptions of New Species of Mollusca from the 

 Pacific Islands. By W. Harper Pease. 



Pinna trigonalis. 



Shell light, of an elongate triangular shape, shghtly curved, basal 

 margin squarely truncate ; valves elevated at their centre, forming a 

 ridge extending nearly the whole length of the shell, and slightly 

 contracted at the centre of the basal margin. Beaks ribbed and stri- 

 ated transversely, striae raised, fine and rather distant, ribs extending 

 down on the posterior margins the whole length of the shell. Horn- 

 colour, darkest at the beak, shading off into white towards the basal 

 margin. 



Hab. Kingsmill Islands. 



Helix acetabulum. 



Shell small, planorboid, slightly convex above, or plane; umbilicus 

 wide, cup-shaped, finely radiately striated above and below, carinately 



