CANCER PAGURUS. 149 



The Craw-fish inhabits the rivers of Europe, especially such as 

 have a clayey bottom. It is found in many of the rivers in 

 England, forming its holes in their banks. It sometimes, though 

 very rarely, attains the size of a moderately small lobster ; more 

 frequently it scarcely exceeds four or five inches in length. The 

 rostrum is projecting and dentated laterally, with one large tooth 

 on each side at the base. The exterior antennae are simple and 

 longer than the body ; the thorax is smooth ; as is also the back, 

 with two small spines on each side ; the abdomen is flat, with the 

 sides of its segments sharp. The large claws are beset with small 

 tubercles ; the two first pair of legs, as Mr. Pennant observes, are 

 clawed ; the two next subulated ; and the tail consists of five joints, 

 with the lamellae rounded. The colour, when alive, is olivaceous 

 or dark brown. 



In the stomach of this species are found the concretions impro- 

 perly called crab's eyes. They are generally about the size of peas, 

 whitish or reddish, roundish, of a laminated texture, inodorous and 

 insipid. They consist principally of carbonate of lime, with a small 

 portion of phosphate of lime and animal gelatin. Crab's eyes are 

 said to be procured in the greatest abundance at Astracan, where 

 the Craw-fish are bruised with mallets, and allowed to putrify, 

 after which the stones are picked out and prepared for use by levi- 

 gation and washing. 



Medical Properties and Uses. — These concretions are medi- 

 cinally employed as an antacid in dyspepsia, diarrhoea, and other 

 diseases attended with acidity of the primes vice. They are rarely 

 met with genuine, being counterfeited with pipe-clay or chalk, 

 mixed with gelatin. The dose is from one to two drachms. 



Off. Prep. — Cancrorum lapilli prseparati. 



CANCER PAGURUS. 



The common Crab. 



Gen. Char. External antenna short, inserted between 

 the inner canthus of the eye and the front ; internal 



