212 G. LINDSTROM, ON THE 8ILUliIAN GASTUOruUA AND PTEROroDA OF GOTLAND. 



Plate III. 



Fi^. 1 — 5. Tnjblidium reticidatum n. p. 55. Fig. 1 A 2 microscopical vertical and horizontal section.s of the 

 shell, showing its strata perforated by tubes of unknown, parasitic organism, f. 3 another 

 vertical section, f. 4 vertical section with apparently tubular structure, formed by small de- 

 pressions or pits on the surface of the shelly strata, f. 5 surface of shell from the margin 

 of the aperture, magnified; the elevated, white dots being the filled up tubes of the parasitic 

 organism. 



» 6—0. Platjiceras cornutum His. p. 63. Fig. 6 from Klinteberg, with aperture evidently moulded 

 after the surface of some other organism on which it had been fixed, f. 7 — 9 from Wisby. 



» 10 — 18. Platyceras prototijpum Phill. p. 67. Fig. 10—10 a from Klinteberg, f. 11 — 12 from the shale of 

 Wisby, identical in ornamentation with specimens of Platystoma niagarense, f. 13 — 14 

 from the hill of Sandarfve, f. 15 ornamentation of the same and profile of a transverse ridge, 

 f. 16 a pair of its apertural lanielLx, f. 17 vertical section of seventeen lamclhe, as they 

 were left in situ imbedded in soft limestone, slightly magnified, f. 18 one of the laraellie 

 highly raagnificd to show its intimate structure. 



1) 19 — 26. Platyceras cornutum His. p. 63. Fig. 19 — 22 vertical sections of the shell, f. 23 interior surface 

 of the shell seen under the microscope; f. 24 part of the same still more magnified, f. 25 — 26 

 horizontal sections of the shell. 



» 27 — 31. Oriostoma helicinum n. p. 170, from the canal near VVestbos in Hall. 



)) 32 — 34. Craspedostoma spinulosum n. p. 182, from Hoburg, f. 34 nat. size. 



» 35 — 38. Relleroplion sphcera n. p. 74, from the shale of Wisby. 



» 39 — 40. Tremanotus longitudinalis n. p. 86, from Lutterhorn in Faro, with apertural expansions left in situ. 



