194 systematic arrangement 



7. Xanthonklla. 



Head disk small, broad in front, narrow, bifid behind. Eyes ses- 

 sile, in middle of disk. Mantle covering the edge of the shell. 

 Foot elongate, oblong ; sides reflexed, rounded, enclosing the body, 

 leaving a posterior branchial opening. Shell partly exposed, thin, 

 horny, scarcely involute, without any spire. 



I. X. lutea, t. 59. f. 8. 



8. Glauconella. 



Head disk moderate, acute in front, truncate behind. Eyes in 

 middle of disk. Mantle enclosed. Foot oblong, broad ; sides bent 



up, enclosing part of the shell. Teeth ? Shell exposed, oval, 



depressed, thick, green ; apex with the rudimentary spine forming 

 a cup-like disk behind. 



1. G. viridis, t. 59. f. 5 



2. G. glauca, t. 59. f. 3. 



3. G. Adamsii, t. 178. f. 1. 



9. Scaphander. 



Head disk large, elongate, subquadrate. Eyes none. Mantle en- 

 closed. Fopt short, rather broad, with narrow reflexed sides. Teeth 

 in two longitudinal series. Shell external, ovate, convolute, striated ; 

 spire small, concealed ; aperture large, narrow behind. 



1 . S. lignarius. Bulla 1., t. 60*. f. 5 ; Forbes Fig. 108.— Teeth of 



§• Hartley, B.M. t. V.V. f. 5. Scaphander lignarius. 



2. ?S. — — ? t. 132. f. 3. 



Lateral tooth of Scaphander lignarius sin- 

 gle, claw-like, crenulated on the posterior 

 margin before the tip ; on the outside winged 

 with a crest on the basal part (fig. 1 08) . — Lovin. 



§§ Teeth in three longitudinal series (fig. 109). 



Fam. II. AMPHISPHYEADtE. 



Teeth in three longitudinal series, forming straight cross series ; 

 the central tooth broad, square ; the lateral curved, bent down. 



1. Amphisphyra. 



Animal enclosed in the shell, thick, broad. Head broad, short, 

 transverse. Tentacles short, conical, far apart, lateral. Eyes mi- 

 nute, immersed, remote, posterior. Lips tumid, forming an inflated 

 vertical mouth, impressed in front. Foot shorter than the shell, 

 subquadrate, dilated in front, truncate, divided into two lobes by a 

 medial slit behind; edge of mantle thickened. Shell bubble-like, 



