NO. 1139. DEEP-WATER MOLLrKCAVKIiKII.L .IXI> BUSH. 833 



pectin idial teeth obsolete. The shell has a prismatic structure. Inter- 

 nal lira 1 and auricular crane well-developed. 



The structure of the animal was described by Mr. Ball as very dif- 

 ferent from that of typical Ammium. According to his description it 

 has a single pair of gills, with long, simple, separate filaments. The 

 foot is slender, with a byssal groove; the end is much enlarged, with 

 an oblique, expanded, concave terminal disk, striated within. Xo 

 labial palpi. Ocelli without pigment. 



A specimen, well preserved in alcohol, examined by us, had two ro\vs 

 of long, slender, reflected gill-filaments, as usual in this family. They 

 were attached to a broad basal membrane, with a free, lanceolate, pos- 

 terior portion. Two pairs of broad, foliaceous, incurved palpi, tinged 

 with dark brown. Those of the anterior pair are united into a hood 

 over the mouth; the others are smaller, curved inward, somewhat lan- 

 ceolate at the tips. No ocelli could be found. The pallial tentacles are 

 all in one row, numerous, of various sizes; from four to six large ones, 

 with as many alternating small ones, correspond to each larger undu- 

 lation or scallop of the mantle-margin. No guard-tentacles. Muscular 

 pallial border is broad, thickened, radially striated, forming a ridge, 

 as preserved, but not tentaculated. Free portion of rectum long and 

 slender. 



A synopsis of the Pectiuida? was recently published by Dr. Frederico 

 Sacco. 1 



He recognized three genera : Chlamys, A-HIHNX/HID, and Pecten, with the 

 same types given by Verrill. Under Chlamys he gives nine subgeuera. 

 Of these, four Chlamys (restricted), Hinnites, JEquipecten, and Palllo- 

 lum correspond with the groups of the same name given by Verrill; 

 Fdlpcs Locard (type, pcsfelis L.), Peplum Buccjuoy, Dant/enberg, and 

 Dollfus, 1889 (type, inflexum Poll), Macrochalinis Sacco, 1897 (type, latix- 

 sinid Brocchi), Flexopecten Sacco, 1897 (type v //e.ro,s'sPoli), Lissochlamis 

 Sacco, 1897 (type, excisti Bronn), are additional to those given by Verrill. 



Under Amussium he has, besides the typical group, four subgenera. 

 Of these, t\vo are new Parvamussium Sacco, 1897 (type, duodecimlamel- 

 latum Bronn), Variamussium Sacco, 1897 (type, cancellatum Schmidt). 

 The two others are Propeamussium and Pseudamussium. 



The three ue\v subgenera of Pecten are Amiixsiopecten Sacco, 1897 

 (type, bnrdiyalensis Lamarck); Oopecten Sacco, 1897 (type, rotinnltdHH 

 Lamarck); and FlaheUipecten Sacco, 1897 (type, fldbelliformis Brocchi). 



1 ISolletino del Mus. Zool. ed Anat. Comp., Univ. di Torino, XII, p. 101. It was 

 apparently issued at about the same time as that by Professor Verrill, here 

 abstracted. 



Proc. N. M. vol. xx 53 



