336 PROCEEDINGS OF THE NATIONAL MUSEUM. 



vol.. XXVI. 



from horizon to horizon, he has found the minor divisions of very 

 great assistance, the more thorough scrutiny and study which they 

 naturallv require, and which is irksome to superficial students, ])einij;- 

 essential to really thorough work in paleontology, and no small help 

 in handling the recent forms. On the other hand, those whose studies 

 do not require this insistence on apparently minor characteristics do 

 not need to use the sectional names, and may easily fall hack on those 

 names by which the larger groups are called. 



The family Veneridte represents the culmination of Pelecypod evo- 

 lution, so far as this may be represented by any single family. In 

 beauty of color and delicacy of color pattern, in multiplicity and 

 variety of sculptural developments, in wide distribution and bathy- 

 metric range, the Veneridte equal if they do not surpass an}' other 

 Teleodont group. While the shells are often exquisitel}^ beautiful, 

 the coloration and appendages of the soft parts are also frequently 

 similarh^ attractive, leading to wonder wdiy parts which are ahvays 

 covered by the mud or sand or hidden between the valves should 

 develop such beauties. The periostracum is usually thin and incon- 

 spicuous, but sometimes b}" color or quality of surface adds attractive- 

 ness to shells otherwise dull or colorless. 



The geographical distribution of gi'oups in the VeneridtB has some 

 marked characteristics, which are especially brought out when the dis- 

 tribution is scrutinized by the minor groups, such as sections. Omit- 

 ting fossils, which in the main agree ver}^ closely with the recent 

 species in distribution, Sunetta and the whole group covered by 

 Gafrarlnm and Lioconcha^ except the section Gouldia; Meretrix, and 

 most of the sections of Cytherea^ except Cytherea and Yentricola^ 

 Mysia^ Gom/pldna^ Macrldiscus; most of the sections of Katahj.'da, 

 and all the great group of Paphla^ except the usually dull and unat- 

 tractive PrototJuica^ are unknown in the waters of the New World. 



On the other hand, Transennella, Pachydesina^ Ilysteroconcka^ Cycll- 

 nella^ and Parastarte appear to be exclusively American. EutheJa 

 and EucaUista belong to the southeastern shores of America, Liocyma 

 to the boreal seas, Saxidomus and Protothaca to the west coast of 

 America, with slight extensions to northeastern Asia and Australasia. 

 Ventis is originally and typically American, with one emigrant in 

 northern Japan. Gemma and Psepliidia agree in the main with 

 Venus. No member of the group of Circe or Gafrariam occurs on 

 the Pacific coast, though I anticipate that Gouldia will turn up there 

 sooner or later. Chionella^ Pitaria^ Katalysia^ and Yenerxipis are 

 almost ubiquitous. Of the Dosiniinaj onl}' Clementia and Dosinidia 

 are know n to be residents of America. In harmony with the late 

 development and specialization of the famih' is the fact that of the one 

 hundred and thirty-seven species known as American onlv tw^o exist 

 on both shores of North America. Eighteen species extend through 



