THE NAUTILUS. 



117 



hinge, in profile, is somewhat like that in fig. 7, but of the 

 laminae little is to be seen but the small, pointed cusps not 

 much larger than the cardinals. 



Fig. 7. P. ovum Sterki (Montana, Alaska), hinge viewed 

 from below. 



Fig. 8. Cardinals of P. dubium Say. 



Fig. 9. Very young nepionic mussel of Sphccrium stami 

 neum Conrad, 0.6 mm. long, showing the valves deposited on 

 the continuous shell membrane, the very short ligament, arid 

 the primitive hinge plates; very fine and slight radial lines 

 are seen on the beaks of most Sphasriida?. 



Fig. 10. Nepionic of the same, somewhat more advanced, 

 1.3 mm. long; the cardinals are just beginning to form on 

 the plate. 



Fig. 11. Young nepionic hinge of Sphcerium occidental? 

 Prime, viewed from below in the open mussel ; the cusps of 

 the lamina? are just beginning to form and are smaller than 

 the cardinals; alii is very small and remote from C3, which 

 is plainly complex ; pill is not yet formed. 



Fig. 12. Musculium transversum Say, nepionic, at an early 

 stage ; the plates are somewhat too broad. 



Fig. 13. Musculium sp., cardinals. 



OBSERVATIONS ON THE NOMENCLATURE OF SLUGS. II 



BY H. A. PILSBRY 



The notes on this subject in the January NAUTILUS, p. 77, 

 provoked several letters on the subject, bringing out facts 

 which materially alter the tentative conclusions of that paper. 

 Mr. Tom Iredale, who has run to earth so many stray names, 

 writes as follows : 



''Upon investigation I find that when Ferussac introduced 

 Arion (Hist. Nat. Moll., Vol. II, pt, I, 1819, p. 50), dealing 

 with the anatomy on p. 67 he wrote: 'L'on peut consulter 

 d'ailleurs, pour se convaincre de leur analogic, les descrip- 

 tions que Swammerdam a donnee de I'anatomie du cochlea 

 nuda domestica, et du cochlea agrestis sive viarum, types de 

 ces deux genres.' 



"As Ferussac had previously cited Swammerdam 's two 



