I'ROSOBRANCHIATA. 



78; 



In Subulites (? = Polyphemopsis, Portlock) the shell is elongated, 

 slender and fusiform, with a smooth surface and a shallow suture. 

 The shell is thin and fragile, and is truncated 

 or rounded in front (fig. 689). The aperture is 

 long and narrow ; the outer lip is thin, and the 

 inner lip is involute ; and there is a distinct 

 notch in front. The range of the genus is from 

 the Ordovician to the Carboniferous. The genus 

 Eu chrysalis, ranging from the Silurian to the 

 Trias, closely resembles Subulites in the shape 

 and other characters of the shell, and is, perhaps, 

 hardly separable from the preceding. Lastly, in 

 the Ordovician genus Fusispira (fig. 690) the 

 shell is fusiform, with an elevated spire and con- 

 vex whorls. The aperture is oval or elliptical, 

 and is prolonged below into a shallow canal ; 

 while the columella is twisted, but is without 

 folds. 



Family 32. Xerixeid.e. — In this family the 

 shell is turreted, thick, and solid,- and the aper- 

 ture is canaliculated in front. The outer lip is terebri/o 

 acute, and is sinuated superiorly or posteriorly, $££ ^gj h America ' 

 a slit-band which runs continuously below the 

 suture being thus produced. The columella and parietes of the 

 aperture are furnished with continuous folds, which are prolonged 



Fusispira 

 Ordo- 



Fig. 691. — Xcri?iea 

 bisulcata. Chalk. In 

 the lower part of the 

 specimen the shell is 

 preserved, while the 

 upper part shows the 

 cast of the interior. 



Fig. 692. — Xerinea Goodhallii, 

 one-fourth of the natural size. 

 The left-hand figure represents 

 a vertical section of the shell. 

 Coral Rag, England. 



into the interior of the spire. All the members of this family arc 

 extinct, and all are confined to the Secondary period. 



