Explanation of Plate XXXIV. 



Pig. 18. Tliiiiolitf! from Blaclc Rock Desert (nilneed iiiir-liuli), llic iiidiviiliial crystals running oft" into 

 a compact stony lufa, so tliat tlif ni.ass from aliovc Las a canlillowcr-likc form. 



Figs. 19 and iO. TLiuolilc from Mono Lake, California (natural size), sliowin;;- tlio gronping of the 

 comi)08ite crystals. 



Pig. 21. Thinolite from Mono Lake (natural size), fragment of a largo composite crystal, made np of 

 small .acicular crystals in i)arallel position. 



Pig. 2"2. Transverse section of tlie crystal represented in Fig. 21, showing the same skeleton structure 

 distinct in crystals from Pyramid Lake (Figs. 2, ;5, etc.). 



Figs. 23 and 24. Group of tbinolite cryst.als from Mono Lake (natural size), showing the .acicular form, 

 and also the way in which the crystals are coated over with secondary carbonate. 



Pig. 25. Group of small crystals (magnified 4 times) from Mono Lake, showing the same method of 

 grouping common in the Sangerhausen pscudomorphs, as shown in Fig. 2(). 



Fig. 26. Group of Sangerhausen pseudonmrjdis (natural size) ; compare Fig. 25. 



Pigs. 27 and 28. I.solated thinolite crystals (maguitied twici^), showing resemlilance in form and sur- 

 face marking to Saugerhanseu crystals ; compare Figs. 31 and 32. 



Fig. 29. Thinolite crystal (natural size), showing cap-iu-cap pyramidal structure, similar to Figs. Id 

 and 17, Plate II. 



Fig. 30. Thinolite crystal (magnified 4 times), showing resemhlance in form to the Saugerhanseu 

 pseudomorphs ; compare with Figs. 'M, 32, and 38. 



Figs. 31 and 32. Single Sangerhausen crystals, showing form and external markings; Fig. 31, natural 

 size ; Fig. 32, magnified twice. 



Fig. 33. Group of small thinolite crystals (magnified 4 times); comp,are with Fig. 2fi. 



Figs. 34 and 35. I'seudomorphous crystals, consistnig of granular calcite from Astoria, Oregon ; copied 

 (reduced one-halt) from figures by ,1. D. Dana in the (Ecology of U. S. Exploring Exi)e<lition, p. C.5(i. 



Figs. 30 and 37. Pseudomoriihons crystals, consisting ol granular calcite, from New South Wales; 

 copied (reduced one-half) from figures by .1. D. Dana in the Geology of the U. S. Exploring Ex- 

 pedition, p. 4H1. 



Fig. 38. Pseudomorphous crystal (natural size) from Rating, Silesia. 



