MONTACUTA. 95 



The only set-off to our chagrin in being compelled to form 

 two new families is, that they will acquire a lasting fame by 

 their titles, in conjunction with the present generic ones, by 

 ministering double honours to two of the most eminent British 

 naturalists, Montagu and Turton. 



We have already, in our preliminary remarks on the Kel- 

 liada, accounted for the disposal of the Montacuta bidentata, 

 formerly of this family, by its transference to the Anatinidte ; 

 and we now state that the third and last member of Monta- 

 cuta, the M. ferruginosa, Brit. Moll. ii. p. 72, pi. 18. fig. 5, 

 5 a and 5 b } is consigned to the company of its congener, for 

 the reasons stated under Anatina. 



MONTACUTA, Turton. 

 M. SUBSTRIATA, Montagu. 



M. substriata, Brit. Moll. ii. p. 77, pi. 18. f. 8 and 8 a; (animal) 

 pl.O.f. 2. 



Animal suboval, thick for its size. It has an oblique out- 

 line, the longitudinal measure being greater than the trans- 

 verse ; the body and mantle are pale yellow, the liver dark 

 green; the mantle has a simple margin, and is largely 

 open ventrally for the passage of a hyaline foot, that has a 

 byssal groove at the heel, from which strong coarse filaments 

 issue, and attach it to the ordinary habitat, the spines of the 

 Spatangus purpureus : all the observed specimens were thus 

 attached, and could not be removed without injuring the 

 animal or shell. They were cut off by scissors, and on being 

 placed in a watch-glass of sea-water immediately protruded 

 the large foot, far exceeding in length the shell; it is mus- 

 cular, raised in the centre, bevelled on each side to a fine awl- 

 shaped edge, and tapers to a very rounded termination, not 

 showing a trace of the lanceolate point. Locomotion would 

 appear to be incompatible with the apparently fixed habitat, 

 but it, as well as the other byssal bivalves, has the power, 

 which we have seen them exercise, of changing place. When 

 the animal marches the foot is extended, and its rounded ter- 

 mination is instantly fixed to the vase in which it is deposited; 



