C. E. Beecher — Koninchina and related Genera. 211 



symmetrically developed. Looked at in the direction of the 

 twinning axis they have an hexagonal outline, showing a short 

 hexagonal prism of the second order in combination at one end 

 with a simple rhombohedron and at the other with two rhom- 

 bohedrons in twin position. This adaptation of a hemiht'dral 

 tetragonal mineral to hexagonal, rhombohedral symmetry is 

 certainly very remarkable and reminds one of the tendency of 

 the isometric copper to develop in a similar way.* 



Fig. 9 represents a crystal with very remarkable habit, which 

 is in the Bement collection. It is striated, ronnded and oxi- 

 dized, so that only a general habit is preserved, which reminds 

 one at first of a complicated fourling. No twinning, however, 

 could be detected and a simple distortion or elongation of the 

 form shown in fig. 4 in the direction of the octahedral axes 

 seems to explain this curious development. For simplicity 

 sake the figure was drawn on isometric axes with a parameter 

 a: a :2a. A less symmetrical development of this same kind 

 gives rise at times to very curious forms. 



Pyrite and chalcopyrite crystals occur intimately associated 

 with one another at the locality. Some of the latter are coated, 

 in part, with a very thin layer of pyrite crystals, but no definite 

 orientation of the two crystals could be detected. It is cer- 

 tainly very remarkable to find at this one locality pyrite crys- 

 tals imitating tetragonal and orthorhombic symmetryf and 

 chalcopyrite imitating isometric and hexagonal-rhombohedral 

 symmetry. 



Mineralogical Laboratory of the Sheffield Scientific School, 

 New Haven, April, 1890. 



Art. XXYI. — Koninchina and related Genera ; by Charles 

 E. Beecher, Ph.D. (With Plate II.) ' 



During the year 1864, Professor O. C. Marsh made exten- 

 sive collections from the celebrated locality, St. Cassian, in the 

 Upper Trias of the Tyrol. All these specimens he has recently 

 placed in the hands of the writer for investigation. They 

 have been examined at the present time with special reference 

 to the brachiopods, which form one of the interesting groups 

 of this remarkable fauna. 



The series of specimens representing the peculiar genera, 

 Koninckina and Amphiclina are rich in numbers and complete, 

 in the later stages of growth, besides furnishing some younger 

 shells, which exhibit a few phases in development of consider- 

 able interest and importance. A critical study has resulted in 



* This Journal, III, xxxii, 419. f Loc. cit. 



