SALPINGOSTOMA ASTEROIDEUM. 75 



peristome thin, the outer portion slightly sinuate. Inner whorls with a slit-band 

 which is replaced in outer half of last whorl by a long narrow slit not extending 

 to apertural expansion but closed some distance behind it. Surface marked with 

 simple or sublamellose transverse growth-lines or rugge and with more or less 

 oblique irregular sometimes interrupted or wavy revolving lines. 



The relations of this genus and the usage of the name Salpingo stoma are dis- 

 cussed by Koken, 1 Ulrich and Scofield,' 3 and Perner. 3 The definition given by 

 Ulrich and Scofield and the limitations assigned by them to the genus are here 

 adopted. The type-species is 8. megalostoma, Eichwald,of the Russian Ordovician, 

 The true position of Salpingostoinn in the scheme of classification adopted in this 

 Memoir is somewhat doubtful, but it may be provisionally assigned to the group 

 Fissidorsata. 



1. Salpingostoma asteroideum, sp. nov. Plate XI, figs. 22, 23 ; Plate XII, 



figs. 1,2. 



Specific Characters. — Shell of 2 — 2-1 whorls, loosely coiled, in contact but not 

 overlapping, rapidly increasing in size (especially in height) to mouth, Avhich is 

 suddenly expanded at right angles to plane of shell to about three times the width 

 of outer whorl. Outer whorl rounded, with weak dorsal carination developed 

 especially near mouth, but elsewhere with subcircular cross-section, increasing 

 rapidly in height near mouth. Umbilicus deep, open, exposing inner whorls, with 

 centre at about one-fourth height of shell. Mouth immensely expanded, sub- 

 circular, rather higher than wide, with inner lip reflexed and extending below base 

 of whorls ; width of mouth about three times that of outer whorl ; outer lip with 

 small central emargination. Surface of shell covered with coarse strong, gently 

 arched rounded rugas regular and equidistant, meeting carina at 60° — 75°, becoming 

 weaker near mouth and dying out on expansions of peristome, with fine weak 

 sinuous revolving spiral lines over the whole shell diverging slightly on each side 

 from carina near aperture. Dorsal slit very narrow, usually concealed by carina. 



Dimensions. — -Width of mouth about 35 mm. ; height of mouth about 40 mm. 



Horizon. — (1) Drummuck Group (Starfish Bed), Upper Ordovician ; (2) Upper 

 Bala Beds. 



Locality. — (1) Thraive Glen, Girvan ; (2) ? Tyrone. 



Remarks. — The types of this species come from Thraive Glen and are in 

 Mrs. Gray's Collection. The immensely expanded mouth and the few whorls and 

 ornamentation closely resemble S. grande (Barr.), 4 from stage D in Bohemia, and 



1 Koken, ' Gastrop. Bait. Untersilur.,' p. 131. 

 - IJlrich and Scofield, op. tit., pp. 851, 897—900. 



3 Perner, op. cit., p. 96. 



4 Perner, op. cit., p. 97, pi. lxxxiv, figs. 12—14; pi. lxxxv, figs. 22—32 ; text-fig. 69a-/. 



