INVERTEBRATE PALAEONTOLOGY. 249 



belong In the genera Pleuromya, Platymya, Myacites, and other groups of the 

 Anatinidee. In the Cretaceous rocks, however, we meet with other species, 

 which, so far as is yet known, seem to belong to lliis genus. It also occurs 

 in the Tertiary rocks, and is now represented by a number of living species 

 in our existing seas. If all of the Cretaceous species, however, that seem 

 (indistinguishable from this genus, really belong to it, it would appear to have 

 attained its greatest development during that epoch. 



The living species of this genus have a wide geographical distribution, 

 and are usually found burrowing in sand at and near low water. G. 

 Australis is said to penetrate sandy bottoms to depths of several feet. 

 The shells of G. glycimeris sometimes attain a length of six to eight inches 

 (Woodward). 



The name Glycimeris, which, it seems to me the rules of nomenclature 

 will compel us to retain for this genus, has, unfortunately, been applied (with 

 slightly-varied orthography) by different authors to widely different genera. 

 It was used as far back as 1553, by Belloni, for a group which, according to 

 Herrmannsen, included only Nucula and Pectunculus, Lamarck. Klein was, 

 I believe, the first author who applied it to a group including the genus here 

 under consideration, along with species of Mya and Lutraria. As neither ol 

 these authors, however, come within the binomial rule of nomenclature, they 

 cannot, I should think, be properly regarded or quoted as the founders of 

 genera. 



In 1799, however, Lamarck applied it, in a strictly binomial sense, to the 

 genus here described, and cited, as the typical species, Mya glycimeris. 

 Consequently, I regard him as the founder of the genus, and that species as 

 its type. It is true, he afterwards used the name for another genus, in 1801, 

 and at a later date, and was followed in this by many authors ; while he also 

 subsequently adopted Menard de la Groye's later name Panopeea for the 

 genus here under consideration. But I do not see how that alters the case 

 in the least; for, when an author once regularly publishes a new genus, 

 designating a well-known species as its type, he has no further control over 

 il, and can only modify or cancel it under circumstances where it would be 

 admissible for any one else to do so. If his typical species, as proposed in 

 1799, had proved to belong to an older genus, so that his Gycimeris of that 

 date became a synonym, then, he might, according to the rules of many 



naturalists, have used the name for another genu>; hut this was not the case. 

 32 h 



