192 MACROSCHISMA. 



somewhat convex ; radiately ribbed, ribs made irregular by irregular 

 growth wrinkles ; anterior ribs alternately large and small. Per- 

 foration wedge-shaped, its length contained about 4 J times in that 

 of the shell. Color whitish, obscurely concentrically clouded with 

 yellowish, and having riblets at intervals speckled with brown. 



The peristome curves strongly upward posteriorly, and this end is 

 more bluntly, broadly rounded than the other. 'The front end is not 

 curved upward. The radiating riblets are much stronger on the 

 long anterior slope, and alternate with much smaller ones ; they are 

 rendered uneven by irregular growth-marks. The orifice is on the 

 posterior slope, which below it is broadly eroded, the erosion not ex- 

 tending, however, to the posterior edge of the shell. Inside it is 

 white, except a tract on each side and in front of the fissure, which 

 is pink. The fissure is double as long as its greatest width ; it is 

 surrounded by a callus, wide except on the back margin. Muscle- 

 impression narrow, deeply impressed, especially posteriorly. 



Length 27 h breadth 14, alt. 8-9 mill. 



Tasmania* 



M. Tasmania Sowb. Thes., p. 206, f. 223.—/ M. Tasmania Gray, 



Angas, List of addit. sp. Marine Moll. S. Australia, in P. Z. S. 1878, 



p. 868. 



M. maxima A. Adams. PL 62, fig. 22. 



Shell oblong, ornamented with little-elevated, subrugose riblets 

 and obsolete concentric stria? ; radiately maculated with brown. 

 Back elevated, sides planulate, front extremity rounded ; posteriorly 

 elevated, subtruncate ; foramen dilated, excavated posteriorly. (Ad.) 



Hakodate, Japan. 



M. maxima Ad. P. Z. S. 1850, p. 202 ; H. & A. Ad., Genera Rec. 

 Moll, iii, t. 51, f. 5.— Dunker Ind. Moll. Mar. Jap., p. 150.— Fis- 

 surella macroschisma Chemn., Schrenck, Reisen u. Forsch. im 

 Amur-Lande, ii, Moll, des Amurlandes etc., p. 308. 



The original description and figure are given. The name macro- 

 schisma has been applied to this species by some authors, but a glance 

 at the figures in Chemnitz, and in Sowerby ( Genera, Conch. III. and 

 Thesaurus) show that at least two species have been confused under 

 that name. Enquirers into the involved synonymy should consult 

 Schrenck and Dunker (7. c), but bear in mind that these authors 

 have not properly discriminated between the two species mentioned 

 above. It has not seemed expedient to give full references, at the 

 risk of still more mistakes. 



