626 Appendix to Part II. 



Lucira excextrica. — G. B. Sowerby, PI. V. fig. 21. 



Testa subovali, leviter incequivalvi, Icevi, umbone adunco, postice 

 sulco prof undo ab umbone ad marginem infer am posticam de- 

 current e in altera valvd, minus prof undo in altera: long. 1*9; 

 lat. I* ; alt. 2' poll. 



Like Lucina C/iildreni, the two valves are somewhat unequal, 

 and sometimes the right, sometimes the left, valve is the larger. 

 The posterior dorsal groove is nearer the edge and deeper than 

 in Lucina Pennsylvanica, and the whole shell is much less 

 orbicular. The present species may be regarded as obliquely sub- 

 oval 



Port Famine, Tierra del Fuego. 



Spirifer Chilexsts. — PI. Y. figs. 15, 16. 



Shell suborbicular, tumid. Dorsal valve deeper than the ventral ; 

 cardinal area shorter than the transverse diameter of the valve, 

 triangular, concave, bound by angulated margins. Perforation 

 lanceolato-triangular. Centre of the dorsal valve with a rather 

 deep and broad sinus, ichich, as well as the side, is furrowed and 

 ribbed. Ribs simple (about twenty-six, of which four belong to 

 the sinus), becoming obsolete towards the angles of the cardinal 

 area, crossed by strongly marked sinuous lines of growth. Beak 

 very prominent and sometchat incurved. Dorsal valve ribbed 

 like the ventral, four of the ribs being upon the rounded but 

 well-defined mesial ridge. Frontal margin of both valves slightly 

 linguiform. 



There are two varieties of this shell, the one much more 

 tumid than the other. 



Dimensions of largest specimen: breadth, 1~; breadth of 

 cardinal line, 1 T > ; length of dorsal valve, lf^ ; of ventral valve, 

 1 inch ; thickness of united valves, ~ of an inch. 



This shell nearly resembles several carboniferous limestone 

 spirifers. It is also related to some liassic species, as Spirifer 

 Wolcotii. 



Cordillera of Guasco, Chile. 



SPIRLFER LIXGrTFEROIDES. — PI. V. figs. 17, 18. 



Shell orbicular, globose, surface smooth, undulated towards the mar- 

 gin, where there are also a few strong transverse furroics of 

 growth. 1 ~a Ives nearly equal. Frontal margin not projecting, 

 bisinuated. Mesial furrow of dorsal valve shallow, lanceolate, 



