ANTHRACOMYA. 85 



Myadas; and under his observations on Anthracomya senex says : "We cannot get 

 at the interior, but there is not much doubt there is a pallia! sinus; and there 

 were probably long siphonal tubes covered by a thick epidermis, the animal 

 burrowing in the mud as most Myadae do." 1 It is difficult to see why such a 

 relationship should be so strongly insisted upon in the absence of direct evidence, 

 but Mr. Salter held the view that the Coal-measures were a marine deposit, 

 consequently the palaeontology had to be fitted in to suit this opinion. 



The characters on which Mr. Salter probably most strongly relied for the 

 reference of these shells to the Myadse are the occasional gaping of both ends 

 (but this is not at all of constant occurrence, even in the same species) and the 

 V-shaped markings on the type specimen of Anthracomya senex. He says, speaking 

 of the shells for which he is proposing a new name (p. 230, op. cit.) : " For these 

 the discovery of a common character in the epidermis at length enables me to 

 propose a generic name ;" but beyond stating that the epidermis is wrinkled, he did 

 not in any way say what this common character was. These markings in A. senex 

 are to a large extent accidental and not specific, and this fact will be further noted 

 under observations on this species (p. 111). But a V-shaped arrangement of the 

 periostracum is to be found in some members of the Unionidse 2 from abroad, and 

 is therefore in no way peculiar to the burrowing Myacidse. The absence of a 

 pallial sinus, the simple Unio-like type of hinge-line, erect external ligament, 

 absence of an internal cartilage, the position and shape of the adductor muscles, 

 and the thickened periostracum, all point rather to a connection with the 

 UnionidaB. In common, however, with Carbonicola, Anthracomya has the 

 accessory adductor scars situated above and posterior to those for the anterior 

 adductors, and not, as in recent Unionidse, below and posterior to them. 



In shape the Anthracomyae approach the genus Tridina (Mutela) but are 

 distinguished by the absence of the multidenticulate hinge. 



There is little evidence to be obtained in favour of the view that the Anthra- 

 comya were burrowers. They are very seldom found at right angles to the 

 stratification of the beds in which they occur, but nearly always lie parallel to 

 them ; and, further, they are always associated with byssiferous Naiadites which 

 could not have lived buried in the mud. 



All the early writers referred the shells, subsequently grouped under the name 

 Anthracomya, to Unio, Ludwig recognising the close resemblance to Anodon by 

 referring several forms to this genus, with which there are strong resemblances in 

 shape and hinge-structure ; but there are certain marked differences, the umbones 



1 'Mem. G-eol. Surv. Great Britain;' 'Iron Ores of Great Britain,' part iii ; 'Iron Ores of 

 South Wales,' 1861, p. 231. 



2 Tor example, the species named Unio Vignonianus, U. Kleinianus, and Anodonta rugifera in 

 the Collection of recent shells in the Natural History Museum, South Kensington. 



