58 A. E. Yerrill — Study of the family Pectinidm, 



The expanded end of the foot, in this and some other genera, is 

 probably used as a pushing organ rather than a " sucker," as sup- 

 posed by Dr. Dall. It is analogous to the large pushing disk on the 

 foot of Niicula and Leda. A sucker would not be of much use on 

 the soft mud where many of these species live. 



The type of this genus is from the East Indies ; other large species, 

 closely allied, are found at Japan (^1. Japonicum), and else«vhere. 



A species, referred, at first, by Dr, Dall to A. pleuronectes (L.), but 

 perhaps the A. 3Iortoni, and A. Dalll were dredged in the West 

 Indies and Gulf of Mexico by the " Blake " Exp. The latter ranged 

 from 218 to 1591 fathoms. The former was from 35 to 60 fathoms. 

 Most of the species are from deep water and mud or ooze bottoms. 



Species of the genus occur fossil in Cretaceous and Tertiary rocks. 



Curiously enough, H. and A. Adams did not give the presence of 

 internal ribs as a character of the genus, but based it only on the 

 form of the shell. Accordingly, they included our large American 

 species, C. Clintonius or Magellanicus in the genus Amusium^ from 

 its general external resemblance to shells of that group. It is really 

 much more nearly allied to the typical species of Chlwnys and Pseu- 

 damttshim, so far as the shell is concerned. 



Amusiuni must be restricted to those species having specialized, 

 internal, radial ribs and small auricles. 



Chlamys Bolten. Type, C. Isiandica (Linne). 



Chlamys Bolten, Mus. Bolt., ed. I, p. 165, 1798, restr. ; Fischer (pars), 1887. 

 Fecten (restT.), Schumacher, 1817. 



Pecien (pars) and Chlamys (pars), H. and A. Adams, 1858; Chenu, 1862; Zit- 

 tel, 1881. 



Pecten (restr.), Stoliczka, 1871. 



Plate XYI. figs. 2-5. Plate XX. fig. 9. Plate XXI. fig. 2. 



As stated on a previous page, the original type of this genus is 

 identical with P. Islandicus (Linne). Therefore this should be 

 adopted, without question, as the true type, as has been done by 

 Fischer and others. 



The group called Chlamys by Stoliczka is the same as ^quipecten 

 Fischer, 1866 ; it is usually regarded as a mere section of Chlamys. 

 (See p. 67.) 



The typical species of Chlamys are high, rounded, somewhat 

 oblique, nearh' equivalve shells, with large inequilateral and oblique 

 auricles ; a large byssal notch ; and several pectinidial teeth. The 

 surface is strongly radially sculptured, both with primary and with 



