310 MAZATI.AN UNIVALVES 



Tablet 1499 contains 6 sp. broken so as to sbew tlie internal 

 lamin». — 1500, a mass almost covering Murex princeps, -with a 

 ? Sphaenia in a varical foliation. — 1501, Uvanilla oUvacea, with 

 several specimens attached. — 1502, 2 sp. of U. unguis, do. — 

 1503, Leucozonia cingulata, do. — 1504, 3 sp. Cuma costata, do. : 

 in one, the P. macroi^hragma has been removed, shewing the 

 amount of erosion. — 1505, Rhizocheilus nux. Pisania gemmata, 

 and Columbella fusca, do. — 1506, Omphalius ligulatus and 

 FissureUa rugosa, do. 



Opercula of Vermetidm. 



(a.) Operculum o. "Aletce centiquadra" simile, sed magis 

 regulariter multispirale ; extus pa rum concavum, marginibus 

 anfraciuum IcBvibus, parum extantibus, umbone centrali elevatd ; 

 superjicie cmfr. circiter viii., umboyie iv. instructis ; intus cica- 

 trice magna irregulariter concentrice mgosd. 



Tablet 1507 contains one of three opercula, probably belong- 

 ing to a second species of Aletes. 



(b.) Operculum spirale, corneum, suholivaceum, tenue ; extus 

 parum concavum, marginibus valde tenuibus, haud regularibus -, 

 anfr. circiter \xx. hand distincte dejinitis, haud extantibus, ad 

 apicem haud umhonatum ascendentibus ; intus cicatrice parvo, 

 vix corrugato. 



Tablet 1508 contains two opercula, which probably belong 

 to an Aletes. 



(c.) Operculum haud parvurn, haud regulare, corneum, tenue, 

 diaphanum ; extus subconcavum, laminis parum elevatis, um- 

 bone extante : intus vix convexum, tin's ?concentricis multis 

 subdistantihus, subextantibus, margine parvo ; cicatrice parva, 

 irregulariter concentrice rugosd. 



Tablet 1509 contains an operculum, in poor condition, inter- 

 mediate between Aletes and Vermetus proper ; remarkable 

 for the internal ridges, which are not crowded into the middle 

 portion, and leave a comparatively small margin. 



(d.) Operculum distincte spirale, tenue, corneum, diaphanum ; 

 extus marginibus parum convexis ; lamina concavd solutd, ItBvt, 

 acuta, spirahter ascendente, anfr. internis conveniente, apice 

 parum elevato, vix umbonato : intus parum convexnm, triente 

 intei^d anfr. multis ; trientibus duabus externis anfractu ultimo 

 occupaiis ; cicatrice vix corrugatd. 



