212 G. LINDSTRÖM, ON THE SILUIUAN GASTKOroDA AND FTEROPODA OF GOTLAND. 



Plate III. 



Fig. 1 — 5. Tryblidium reticulatum n. p. 55. Fig. 1 & 2 microseopical vertical and borizontal sections of the 

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

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

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

 of the aperture, raagnified; the elevated, white döts being the filled up tubes of the parasitic 

 organism. 



» 6 — 0. Platyceras cormilum His. p. 63. Fig. 6 from Kliiiteberg, 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 prototypum. Phill. p. 67. Fig. 10 — 10 a from Klinteberg, f. 11 — 12 from the shale of 

 Wisby, identical in ornamentation with speciraens 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 lamelliie, f. 17 vertical section of seveuteen lamellae, as they 

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

 higlily magnified to show its intimate structure, 



» 19 — 26. Platyceras cornutum His. p. 63. Fig. 19 — -22 vertical sections of the shell, f. 23 interiör 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 Westöös in Hall. 



M 32 — 34. Craspeclostoma spinulosum n. p. 182, from Hoburg, f. 34 nat. size. 



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



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



