liovie new ami peculiar Molluscs. 42'* 



both was the saiiu', viz. tlu; " conij)a.s.s-8calloj)," (U- Ostrea 

 pleuroncctes ot' Ijiiuu'. Swainson called it Pleuroiiecfiu : his 

 description, however, is both inade(juate and incorrect ; and 

 that name had been appropriated by Kafincsrjuc to a well- 

 known faniily of fishes. Tne deserijjtions of yl//<«.s'.s/«m and 

 Amiisiiiin ,<,Mven by Messrs. Adams and Dr. Woodward arc 

 also unsatisfactory. The j)eeuliar character of the genus 

 consists in each valve being tinted inside, without any corre- 

 sponding ribs appearing outside as in certain species of Pficten. 

 The use of these internal ribs may be to strengthen and sup- 

 port the delicate fabric of the shell. 



Amu,'isi((m hiciihi/n*, Jeffr. 



Pleuronectia htcida, JeJlr. in Wyville Thomson's ' Depths of the Sea,' 

 p. 4(>1, f. 78. 



SiiKLL rotmdish, with a tendency to become longer and oval 

 in some specimens, equilateral, flattened, very thin, semitrans- 

 parent, and glossy : scufj)(ui'e, in the upper valve none, except 

 fine concentric and close-set lines of growth, which are more 

 consjiicuous towards the outer edge in front ; the lower valve, 

 ■which is much smaller than the other, is marked with regular 

 but croveded concentric strife : colour white : margins semi- 

 circular in front and at the sides, whence there is an abrupt 

 slope to the back: beaks minute and inconspicuous: ears 

 small, nearly equal in size, right-angled : hinqe-ltnc straight, 

 occasionally spinous : cariihif/e-jiit minute, triangular, with a 

 curved base : hinge-plate broad and smooth : inside pearly, 

 furnished with 9 slight and thread-like ribs, which are visible 

 on the outside, owing to the thinness and semitransparency 

 of the shell ; these ribs occupy only the middle of the interior, 

 and do not extend to the umbonal or posterior area, nor in 

 full-grown specimens to the front ; each rib terminates ab- 

 ruptly in a rounded knob or point ; one is in the centre, and 

 the others diverge on either side, the last or hindmost pair 

 forming the base of each ear : muscular scars roundish-oval, 

 situate below the beaks. L. 0"5. B. 0*5. 



Station 12, 1450 fms., lat. 56° 11' N., long. 37°41'W., 

 Globif/erina-oozc and stones. ' Porcupine' Exp., 1869, 557- 

 862 fms. ; 1S70, 500-1095 fms. Gulf of :\Iexico, off Alli- 

 gator Bank, 156 fms. (Pourtales). 'Challenger' Exp., off the 

 Azores, 1000 fms. 



Single valves from all depths are not unfrequently marked 

 in the same way as I have noticed as to Pectcn fragilis. 



* Shininp. 

 Ann. i[- }rng. X. ITist. Scr. 4. Vol. xviii. 29 



