60 MYTILID^E. 



of the ligament, are well developed and of very dark colour. 

 The body is the least I ever saw in so large a shell ; this is 

 occasioned by the ovarium not being mixed up with it, but 

 that organ is spread in great thickness over the major part of 

 the inside of the mantle on both sides, and at the date above 

 noted contains many hundred thousand ova, which at the 

 latter part of the autumn are discharged into the sea, leaving 

 the mantle a white thin membrane, after which the body of 

 the animal increases in bulk and grows fat, becomes edible and 

 in season, which is two months later than the oysters, as they 

 are not considered good until the end of October. 



They are much eaten at Exmouth by the working people, 

 but in some constitutions they have either a deleterious or the 

 opposite quality, a pruriginous effect. 



It is a mistake that the ova are received in any part of the 

 branchiae for protection and maturation for some time pre- 

 vious to ejection, as not one-tenth of the immense masses of the 

 ovarian membranes could be located there; the branchiae, 

 from their smoothness, are very ill adapted for such an asylum, 

 and if they are ever seen there, it is from the unavoidable 

 contact of the ova when in progress of exclusion : the pulli are 

 never seen in the animal in a testaceous state, as in the fresh- 

 water Unionida, but are at once cast to the waves, where they 

 become the prey of various animals ; still, enough escape de- 

 struction to maintain their enormous numbers. The sea in 

 autumn is filled with the ova : at ten miles from land in 14 

 fathoms water, if the fishermen's lobster-pots are left for two 

 or three days, they will be covered with very young testaceous 

 muscles, and in a week or two more than half an inch long ; 

 but the parents never inhabit more than half a mile from the 

 shore; of course the ova are floated out to sea, and sink as 

 soon as they become testaceous. That the animal never 

 carries testaceous pulli is manifest from its being more or less 

 at all seasons edible. Though this is one of the commonest 

 of the bivalves, it is an object of great interest to the mala- 

 cologist from its elaborate organization. I may state that this 

 is amongst the very few marine Acephala which have the 

 ovaria attached more or less to both sides of the mantle ; bv 



