Malformed Crabs

Abstract

IN your issue of March 10 I observe a most interesting letter from your correspondent, Mr. R. I. Pocock, regarding a malformed specimen of Cancer pagurus in the Dover Museum. I have never seen such a remarkable case of malformation in the common edible crab, but in the Robertson Museum here is to be seen a very fine specimen of Nephrops norvegicus, having three digits on the right pincer or great claw. The supernumerary digit, which is fully two-thirds the size of the normal one, springs from the inner side of the base of the inner movable finger, and is sharply toothed on both sides, and directly opposable to the outer finger. The normal digit is fully developed and curves outwards from the supernumerary one at a wide angle, the distance between them being fully three-quarters of an inch at the points. They move together, and permit an opening of about half an inch between the supernumerary and the normal outer digit, so that little or no inconvenience would be caused to the animal during life. This specimen was caught by fishermen in the neighbourhood of Cumbrae, and was given to a Millport gentleman, Mr. Liddle, who kindly handed it over to the Museum.