lU-S 



Ci. LINUSTKOM, ON THE SILURIAN GASTKurOOA AND PTEKUPUlJA OF GOTLAND. 



Irolaiid and Russia. It is conscquetitly oikj of tlie most characteristic Gastropods of 

 the Silurian formation. That there should be a <,freat amount of variation in a form 

 of such wide a horizontal and vertical distribution is nothing more than could be 

 expected. As the iigures show, there are elongated and short forms. The variety 

 from Estlionia, iig. 17, is the shortest and more coarsely striated, the body whorl nearly 

 double the size as the others. Its height is "28 millinL, its breadth 80 mm. The spe- 

 cimens from the limestone of Slite, tigs. 18, 19, are also short and broad reminding 

 of the Devonian form which Hall and Whitfield have called Trochonema rectilatera. 



20. Pleurotomaria qualteriata Sculotheim. 



Helicites qaalleriatus 

 Solariuin f pelrupulitamim 

 EtioiDjiludus qaaltvrialus 



IS'iO. 

 1822. 

 1830. 



1834. 

 1835. 

 1840. 

 1844. 

 1845. 

 1848. 

 1858. 

 1865. 

 1SG7. 

 1869. 



1880. 



1843. 



1848. 



1854. 



1860. 

 Straparollus quallerianus 1850. 



Straparollus •pseiidoquciUeriatiis 1850. 

 liliapliitiloma (jualleiialiim 1859. 



Klphilcta Ollaicensis 1860. 



150, till). 1 f. 3 a— 31), tab. 



Pleurotomaria leiUicularis 

 Euomphaltta ijaalleriatus 



ri. XIU lig. 15—16. 



ScHi.OTU. Petrcf. Kmule, 103. 



Id. Naclitriiije, 61, lab. XI I'. 3 a — c. 



Pander l^uitriiKi! ziir Googii. liusslaiid 



28 f. 14. 

 (loLinuss in Ki.odkx, Vurstciiitr. Mark BraiiJeiiburgs, 155 

 Bkonn Leth. (ieo-jii. l;c Autl. Ikl I, 94, Taf. II f. 1 a, b. 

 EiciiWALD Scliicliteiisyst. Estlaiids, 115. 

 GoLDFUSs Peticfacta Gcrmania; III, 81, tab. 189 f. 3. 

 Veuneuil Russia, vol. 2, 333, tab. 23 f. 1 a — b, 2 a — b. 

 Salter Memoirs Geol. Survey 11, i, 356, pi. XIV \. 7. 

 Friedk. Schmidt Geol. Estlaiuls, 206. 

 Kjekulf Veiviser, 7 

 ToRNuuisT Lagcrioljden i Dalarue, 19. 

 Karsten Vcrsteinerungen ... in Schlesvvig iind 



Hg. 9 a— b. 

 Angelin & LiNDSTROM p. p. Fragmenta Silurica, 



(excl. fig. 12—14). 

 Conrad in Emmons Geol. N. York |)l. II, 392 . .. ^„., 



PI. Icnticularis Hall Pal. N. Y. vol. I, 172 is (|iiite dillcrcnt 

 Bronn Nouieiicl., 480. 



Ferd. Roemer Leth. geognostica ed. 3, 1, i, 459, lab. 2, f. 1 a 

 EicinvALD p. p. Lelluiea rossica I, ii, 114. 

 D'Orbiony Prodr. I, 6. 

 Id. Ibid. I, 30. 



Salter Canad. Organic Remains, Dec. I, 13. 

 Billings Canadian Naluralist, 166, fig. 9 — 10. 



Holstein. 43, tab. 14 



12, tab. XV f. 10, 11 



393 C. 101,2 iV 102. 



-b. 



Shell discoid with short, ilat spire of live and a half whorls. The apic;il side 

 is gently convex or nearly flat and the sutures are very shallow. The whorls are on 

 the und^ilical side more convex, increasing in heiglit and convexity near the umbilicus, 

 which is large and open. 



The angle formed by the slit band is interposed between the umbilical and a|)ical 

 sides and is highly acute, of 80 °. Its limits are designated through the converging 

 threadhne ornamental lines of the surface which for the rest is smooth. The slit band 

 is at largest on the apical side and there separated from the other surface through 

 no distinct bordering lines. The crescents are fine and indistinct. 



As may be perceived from the dimensions given below, the Gotland mutation of 

 this species is more discoid than the older, which are relatively higher in their last whorl. 



