82 LAND AND FRESHWATER 



character alone, species of Ariopluinta and JVilgiria fall into the 

 following groups : — 



A. With narrow median band. With broad median band. 

 a. Median teeth bicuspid. 



Laterals bicuspid A. Icevipcs. 



B. With broad median band. 

 j8. Median teeth bicuspid. 



Laterals aculeate A. c?/><is. 



A. immerita. 

 y. Median teeth tricuspid. 



Laterals aculeate A. inierrupia. 



A. bojadera. 

 A. intumescens. 

 S. Median teeth tricuspid. 



Laterals bicuspid 



N. helangeri {vide Semper). 



A'^. bintrialis. 



N. solata. 



N. tranquebarica. 



N. maderaspatatia {vide Semper). 



iV. ligulata {vide Semper). 



The sinistrorse Helices from the Malay Archipelago placed in 

 Ario2ihanta by Semper, as I have mentioned in Vol, I. p. 133, find 

 no place here. They possess a very different type of radula. The 

 central teeth are either quite plain-sided, as in ampJiidroma, v. Mart. 

 {=zmartini, Pfr.), 7-areguttata, Mull., and nemoi'ensis, Mouss., or with 

 side cusps near the apex, as in striata, Gray, and riimpJd, v. d. Busch., 

 and into this last group comes retrorsa of Tavoy, of which I have 

 examined a second specimen, collected by Dr. Hungerford. Por 

 this group I would propose the subgeneric title Semperia, if not 

 already used. 



EXPLANATION OF PLATE LXX. 



Fig. 1. Crypto&oma imisitatum, G.-A., X 1"5. Eastern Burniah. 



1 a. Ditto, nat. size. 



2. Cry2)tosoma prmstans, GoxxlA, X 1'5. Moulmain. 



2 a. Ditto, nat. size. 



3. Cryptosoma inusitatiim : view of part of left side, X 1'5. 



4. Ditto : the buccal mass from left side, X 4"5. 



5. Ditto : jaw, X 8. 



6. Ditto: central teeth of odontophore; 6a, 17th to 23rd median; 



6 b, the outermost laterals, X 196. 



7. Ditto : generative organs, X 4'5. Lettering as in former Plates. 

 7 «. The albumen-gland and part of hermaphrodite duct, X 4'5. 



7 b. The amatorial organ, X 2'5. 



7 c. Ditto, with fleshy part more exposed, X 4'5. 



8. A sjiiermatophore, X 4'6. 



h.d., hermaphrodite duct ; r.m., retractor muscle ; D., dart or amatorial 

 organ ; s])., spermatheca; v.d., vas deferens ; P., male organ. 



EXPLANATION OF PLATE LXXI. 



Fig. 1. Cryptosoma siainense, Haines, X 1'5. Siam. 



1 a. Ditto, nat. size. 



2. View of part of left side, showing the left dorsal and shell-lobes, 

 X 1-5. 



2 «. Posterior side, foot. 



