British Species of Mytilus. ftf 



2. Mytilus incrassatus. 



M. testa ovali, anterius compressiuscula, margine membranaceo, 

 umbonibus decorticatis, posterius ab umbonibus versus basin 

 gradatim incrassata, ligamento \ aide exserto. 



Tab. V. Fig. 4. 

 Habitat in rivis. 

 Long. 2 poll. 5 lin. Lat. 4 poll. 9J lin. 



A very distinct species ; rough and dark-coloured on the out- 

 side, thicker and stronger than the rest ; the hinge towards the 

 posterior extremity. Remarkable for its large exserted ligament ; 

 and posterior part, in a slope from the umbones to the base, 

 being much incrassated, which gives that part in the inside 

 a white milky appearance ; whereas the rest is of a fine pearly 

 hue. 



In the river Trent at Holme, near Newark, Nottinghamshire. 



The variety of M. cygneus, given by Dr. Maton and Mr. Rack* 

 ett, ought perhaps to be considered a variety of this species . 



3. Mytilus anatinus. 



M. testa ovali, anterius compressiuscula, fragilissima, margine 



membranaceo, umbonibus decorticatis, area\ antica basique 



parallelis. 



Tab. V. Fig. 5. 



Habitat in aquis dulcibus. 



Long. S poll, i lin. Lat. 6 poll. 7i lin. 



The shells of M. anatinus, when they grow to a large size, are 

 proportionably as ventricose as those of M. cygneus. My spe- 

 cimen, the outline of which accompanies this paper, I took many 

 years since from the pond in the garden of my revered friend the 



Rev. William Kir by of Barham. 



4. Mytilus 



