58 M. o. A. L. morch's review of the vermetib.^;, [Feb. 11, 



3. BlVONIA SUBTRIQUETRA, Morch. 



T. valida, later aliter affixa, irregulariter tort a ; anfr. primi litui- 

 formes vel planorbiformes ; carina mediana elevata, compres- 

 siuscula; latere exteimo planiusculo, suhperpendiculari, basi ex- 

 panse, liris plerumque destituto ; latere interno convexiusculo 

 {in junioribus piano), liris 10—12 cequidistantibus ; strice incre- 

 menti leviter sigmoidece ; dissepimenta interna tenuia, convexa, 



Diam. aperturse circ. 1 2 m. 



Var. a. SQUAMIFERA. 



T. carina dorsali parum prominente, squamis paucis remotis com- 

 pressis acutis ; latere interno liris 4-5 validis angustis sub- 

 squamosis, interstitiis lirulis 1—2 incequalibus ; latere externa 

 superne lirulis 2—3. 



Diana, apertures circ. 7.m. 



1 Favanne, La Conchyl. pi. &Q. f. B 2, fem. juvenile ? 



Fossilis in form, tertiaria ad Asti {coll. T. O. Semper). 



This species lias the same relation to B. triquetra as Thylacodes 

 melitensis, Gm., to T. intiotiosa, Salis. 



4. BivoNiA suTiLis, Morch. 



T. affixa irregulariter lituiformis,fere libera; anfr. graciles, primi 

 irregulariter planorboidei, carnei, liris expressis longitudinali- 

 bus alternatim minoribus, submoniliferis, interstitiis granulis 

 validis, remotis, scepe cum lateralibus confluentibus, inde scrobi- 

 culis elongato-quadratis reticulata ; sculptura aperturam versus 

 Icevior vel fere evanescens ; anfr. ultimus solutus, longuSy albe- 

 scens, varicibus duabus majoribus et duabus minoribus. 

 Diam. aperturse et anfr. ult. circ. 3 m. 



Hab. In littore occidental! Americse centralis, in valva solitaria 

 Veneris subimbricatcB Sow. affixa {Mus. Cuming). 



This species is exceedingly like to Bivonia semisurrecta, Biv., but 

 differs chiefly in the catenulated granulations of the furrows and 

 moniliferous appearance of the lirse. 



Var. a. ? major, liris 3-4 validioribus, ubique impresso-punetata . 



Diam. aperturse 7 m, {coll. Dunkeri, 222). 



This specimen, on a fragment of a Pinna, probably from Central 

 America, is very like a large variety of B. semisurrecta in the Mu- 

 seum of Breslau. 



Var. /3. TRiauETRA. 



T. corrodens, irregulariter planorbifoi'mis, triquetra, lira dorsali 

 distincta ; rugce et strice incrementi utrinque sigmoidece ; lirce 

 longitudinales obsoletissimce vel evanescentes. 



Diam. aperturse 5 m. 



Hab. Mazatlan, on a valve o{ a Placunanomia {Semper' s collection 

 at Altona). 



I cannot see any notable difference between var. /3 and Bivonia 



