98 Frederick Chapman : 



Dimensions. — Two specimens from Loyola measure in greatest 

 length, from outer border of spiral to ventral edge, 46.5 mm. and 

 30 mm. respectively. 



Occurrence. — Silurian (Yeringian). In dark limestone, Loyola, 

 near Mansfield. Collected and presented by Mr. G. Sweet, F.G.S. 

 A small example (cast) in ochreous mudstone. Loyola, near Mans- 

 field; G.' Sweet collection. 



Platyceras erectum, J. Hall sp. (Plate V., Fig, 43). 



Platyctras erect mn, Hall, 1879. Pal. New York, vol V., pt. II., 

 p. 5, pi. II., figs. 4-11. 



Observations. — The present specimen is a cast in mudstone of a 

 depressed ovate Platyceras, partially erect in character and with 

 an open spire. The nearest allied species appears to be J. Hall's 

 Platyceras. erectum, found in the Lower Devonian of New York 

 State. 



Occurrence. — Silurian (Yeringian). In yellow mudstone. Parish 

 of ^Vallen, Sect. 44; Geol. Surv. Vict. Bb 15. 



Genus Diaphorostoma, Fischer ( = Platyostoina, Conrad, non Klein). 

 Biaphorostoina retrorugatum, sp. nov. (Plate V., Figs. 44, 45). 



Descrijifion. — Based on a cast of the thin shell. Consisting of 

 four rapidly increasing compressed whorls, forming a somewhat 

 ovoid outline. Spire slightly elevated. Body whorl large. Base 

 narrowly umbilicate. Aperture apparently suborbicular to ovate. 

 Shell surface traversed by well-marked irregular folds or corruga- 

 tions which curve obliquely backwards. 



Dimensions. — Approximate length of shell when complete, 35 mm. 

 . Greatest width, 26.5 mm. Height, 21 mm. 



Observations. — This shell appears to be quite distinct from any 

 figured species hitherto known, but approaches Diaphorostoma 

 lineatum, J. Hall sp.i in general form. That species occurs in the 

 Upper Helderberg limestone of New York, and in tlie Hamilton 

 Group of the western part of the State. 



The Victorian species is distinguished from Platyceras by the 

 large and open body whorl. 



Occurrence. — Silurian (Yeringian). A cast in yellow mudstone. 

 Ruddock's Quarry, near Lilydale. Collected by Mr. R. H. Annear. 



1 PlatyoMoma lineatum, J. Hall. Pal. New York, vol. v., pt. ii., 1S79, p. tl, pi 



