554 



Genus 2. Aplustrum, Schumacher. (Animal, pi. cxix. f. 1. 

 Sliolls, Bulla, sp. 4, 5. pi. cxx. f. 4-7.) 



Animal ut in Hydatina. 



Testa globoso-ovalis ; spira depresso-plana. Apertura oblonga, 

 postice baud coarctata, canali brevi subemarginato; labium externum 

 acutum; labium internum nullum. Columella prominens, invo- 

 luta, tortilis, oblique truncata, margine interno tenuissimo, sub- 

 replicato. Umbilicus nullus. 



Animal as in Hydatina. 



Shell globosely oval ; spire depressly flattened. Aperture ob- 

 longs posteriorly slightly contracted, with a short subemarginate 

 canal ; outer lip sharp, inner lip wanting. Columella prominent, 

 involute, twisted, obliquely truncated ; inner margin very thin, 

 somewhat reflected. Umbilicus none. 



Genus 3. Hydatina, Schumacher. (Animal, pi. cxix. f. 2. 

 SheUs, Bulla, sp. 7-10. pi. cxx. f. 8-18.) 



Caput appendicibus labialibus duabus bifidis ; lobis tentacu- 

 laribus duobus, acuminatis, auriculatis, posterioribus lanceolatis, 

 sursum testam recurvatis ; oculi minimi, nigri, ad basin internani 

 eorum sessiles. PaUium interne tenue, membranaceum, externe 

 crassum, carneum, triangulare, circa spiram convolutum. Pes 

 magnus, tenuis, membranaceus, sui'sum testam recurvatus, antice 

 auriculatus, postice rotundatus. 



Testa ovali-globosa, valde ventricosa; spira depressiuscula. 

 Apertura ampla, postice coarctata; labium externum tenue, acutum; 

 labium internum tenuissimum, replicato-adnatum. Venter im- 

 perforatus, inflatus. 



Head wdth two bifid labial appendages ; tentacular lobes two, 

 pointed, auriculate, posterior large, flattened, lanceolate, recurved 

 over the shell ; eyes small, black, and sessile at their inner bases. 

 Mantle internally thin and membranous, externally thick, fleshy, 

 triangular, curving round the spire. Foot large, thin, membra- 

 nous, recurved over the shell, auriculate in front, rounded behind. 



Shell ovately globose, very ventricose; spire somewhat de- 

 pressed. Aperture wide, posteriorly contracted ; outer lip thin, 

 sharp ; inner lip very thin, reflected over and adnate to the last 

 whorl. Last whorl imperforate, inflated. 



Genus 4. Tornatina, Adams. (Animal, pi. cxix. f. 3. Shell, 

 Bulla, sp. 11-26. pi. cxxi. f. 24-39.) 



Caput subtrigonale, latum, antice rotundatum, lateribus pro- 



