SPECIE* OF PISlDirJI. 79 



named it Peru pulcltella but never published any description. 

 Hence it was left to Jenyns, who recorded it (83, p. 306) as : 



"P. testa, oblique ovali, ventricosa, profundius striata; um- 

 bonibus obtusiusculis, simplicibus." 



Unfortunately Jenyns had associated with it as varieties undoubted 

 examples of P. subtrvncatum and P. milium *, so that his more 

 extended diagnosis made to cover these becomes inapplicable. 



The best specification is probably that by Malm, though the 

 remarks as to coloration do not hold universally (106, p. 89) : 



" G. oblique ovalis, ventricosa, profundius et eleganter 

 striata, nitida ; lutescenti-alba, sed plerumque omnino fusco- 

 cinerea, zonisque 1-4 obscurioribus ; natibus convexis, uin- 

 bonibus prominulis." 



And he further notes : [Translatiou] 



"Outline everj'where well rounded off, no prominent angle 

 at the point of junction of the dorsal with the posterior 

 margin. Total shape oviform, slightly compressed and 

 oblique. . . Apices of the umbones situated rather far back. . . 

 None of the small species has so deep and at the same time 

 so elegantly arranged stria3 as this." 



These deeply cut strise are typical of the species, and impart to 

 its surface an iridescence such as that displayed by Barton's buttons, 

 or Kobert's lines. 



The detailed characters of the hinge are : 



Hinge (PI. IT, f. 1 ; III, f. 8) about f the length of the shell, 

 very strong and wide, projecting well inwards, uniformly arcuate. 



]{. V. a. i. a little more than ^ the length of the hinge-line, strong, 

 slightly curved inwards ; base very strong and swollen ; 

 apex on distal side of centre, not very prominent, obtuse- 

 pointed; ridges somewhat rounded, sloping about 

 equally, and fairly steeply. 



a. ///. about the length of a. r., outwardly inclined ; apex 

 fairly central, prominent, rounded-obtuse ; ridges com- 

 pressed, somewhat sharp, sloping fairly equally, and 

 steeply. 



3. not very prominent, lamelliform, thin, sharp, top flat 

 but slightly crenulated, slightly arcuate, parallel on the 

 whole to the shell-margin, but the extreme posterior 

 end (6) thickened, grooved and deflected sharply 

 inwards. 



* Specimens named P. pukMlum in the Hnnley Collection proved to 

 comprise two examples, very smooth, of that species, with one of P. subtrun- 

 catiim (B.M. 1907.12.30: 516-18) and four of P. millinm (B.M. 1907.12.30: 

 508-11) all marked simply " British " and probably received from Jnyus. 



