58 R. BULLEN NEWTON on 



Family CAPULID^. 

 Crepidula falconer!, sp. nov. 

 PLATE 2, figs. 13, i3a. 



DESCRIPTION. Shell sub-oval, convex, labial side depressed and sub-vertical, 

 opposing side inflated ; nucleus forming a minute post ero- lateral spiral composed 

 of two volutions well divided from the peritreme ; surface striated concentrically 

 and periodically ridged, obscurely and microscopically tessellated, and possessing 

 indistinct radial striations ; aperture oval, extensive, concave, porcellanous, 

 provided with a thin, continuous and rather undulating peritreme, a prominently 

 arched and well sunken septum, having beneath its lateral terminations a pair of 

 oval and concentrically marked muscular scars which are united by a rounded or 

 horse-shoe shaped connexus hidden by the septum. 



DIMENSIONS. 



Adult Young 



Alt. ... ... ... ... 43 ... 9 millimetres 



Lat 27 ... 5 



REMARKS. The foregoing characters have been drawn up from an adult 

 example, although the majority of the specimens are only about half its size, 

 whilst others are of considerably smaller dimensions. This adult form shows a 

 remarkable scar-line on the internal floor of the aperture, pursuing a diagonal 

 course from beneath the septum to the right ventral side, with obscure evidence 

 of a bifurcation about half way. No muscular impressions of this nature have 

 been observed in recent examples like C. fornicata (Linnaeus), the type of 

 Lamarck's Crepidula, nor does there appear to be any reference in literature 

 pointing out the origin of such markings in this genus. It is therefore considered 

 that they must indicate a connection with part of the mantle attachment. A 

 small horizontal slit-like cavity exists behind the central upper surface of the 

 septum, which is probably of umbilical value, although having apparently no 

 opening to the spire, and thus representing a pseudo-umbilicus. The horse-shoe 

 shaped adductor scar with its latero-oval muscular impressions, are very typical of 

 the Family Capulidae, being well marked in Capulus ungaricus (Linnaeus) of 

 Recent seas, the type of De Montfort's genus Capulus. Our new species, 

 however, is a true Crepidula and not to be mistaken for Capulus which 

 possesses no internal septum. The following references to other described forms 



