A. E. Verrill — Study of the family Pectinidm. 81 



Our shell differs decidedly from the original description of 

 P. fragilis. Moreover we have obtained from several stations a 

 shell of similar size, which appears to be the true fragilis, as it 

 agrees closely with the original description. It also closely resem- 

 bles P. pudicus, described by Mr. Smith, from east of Marion Island, 

 in 1375 fathoms. (Chall. Exp.) 



We have but one specimen, which is somewhat broken at the 

 margins. 



Hyalopecten fragilis (Jeffreys) Verrill. 



Pecten fragilis Jeff., Ann. and Mag. Nat. Hist, 1876, p. 424; Proc. Zool. Soc, 

 London, 1879, p. 561, ^ars (not the fig., pi. 45, fig. 1). Yerrill, Trans. Conn. Acad., 

 vl, p. 232, 1885; Expl. by the Albatross, p. 577, 1885. 



This is one of the most simple shells known to me in this family. 



The shell is very thin, hyaline, distinctly undulated, but not 

 otherwise sculptured. No camptonectes sculpture is visible. The 

 edges are very thin, apparently not bevelled. The hinge-plate is 

 thin and delicate, without cross-lines, and with a single faint sub- 

 marginal rib, parallel with the margin ; ligament very thin ; resil- 

 ium very small, in a triangular pit ; no auricular crurae. The ante- 

 rior auricle is well developed, with a deep byssal notch, but without 

 pectinidial teeth ; the posterior auricle is undeveloped. Accord- 

 ing to Friele there are no visible ocelli. This species, which we 

 consider the true P. fragilis Jeffreys, was taken at the following 

 stations : 



Station 2115, in 843 fathoms; 2215, in 578 fath. ; 2221, in 1525 

 fath. ; 2234, in 816 fath. ; 2710, in 984 fath. It occurs off the Euro- 

 pean coasts and northward to the Ai'ctic Ocean, in 656 to 1750 fath. 



Pseudamusium sixaile (Laskey). 



Pecten similis Lask., Mem. Wern. Soc, i, p. 387, pi. viii, fig. 8, 1811. Forbes and 

 Hanley, Brit. Moll, ii, p. 293, pi. lii, fig. 6, pi. S, fig. 1, animal. Jeffreys, Brit. Conch., 

 ii, p. 71; V, pi. xxiii, fig. 5. 



Plate XVII. figs. 8, 8a. 



The shell in this small species is thin, translucent, nearly smooth, 

 symmetrical, broadly rounded, longer than high. The valves are 

 only slightly unequal ; the right valve is a little flattened, and its 

 edge turns up a little so as to fit tightly against the edge of the 



Trans. Conn. Acat)., Vol. X. JuxVe, 1897. 



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