302 MAZATLAtf UNIVALVES 



rum Icevibus, parum elevatis, hand (normaliter) separatis : intus 

 convexiore, cicatr. muse, mediano, circulari, magnd, irregulariter 

 concentrice rugulosa ; marginem versus anfractus monstrantc. 

 Vermetus centiquadrus, Vol. Voy. Ven. pi. 11, f. 1, la, \a bis. 

 + Vermetus Peronii, Vol. loc. cit. f. 3, 3#. 



The operculum appears intermediate in character between 

 the regularly rnultispiral operculum supposed to belong to a 

 species of this group, and the deeply concave, paucispiral 

 operculum of Siphonium giganteum. One specimen found in 

 situ, (by which, along with two others scarcely admitting of 

 doubt, the rest were identified,) has not more than half the 

 diameter of the aperture. Most of the few found were more 

 or less irregular ; the edges having a tendency to separate 

 elevation, and the whirls to become fewer after fracture. 



The V. Peronii, a group of which is figured on Strombus 

 galea, fixing the locality of the species, appears only to differ 

 from V. centiquadrus in the absence of punctures : buL as both 

 states are frequently found on the same specimen, it cannot 

 warrant specific separation. 



The shell is loosely adhering, and of very irregular habit of 

 growth: when spiral, with rapidly diverging whirls. The 

 sculpture is close, and seldom much impressed. The colour is 

 laid on here and there in blushes. An average specimen 

 measures as it stands long. 2 '4, lat. 1*4, diam. '44. 

 Hab. Mazatlan ; not uncommon on Spondylus and Chama ; 



also on stones and other shells ; L'pool fy Havre Coll. 



Tablet 1476 contains an extremely young sp. with apex en- 

 veloped ; also one somewhat older. 1477, a young sp. growing 

 straight, on Conus gladiator. 1478, an adolescent sp. covering 

 an extremely deformed Crepidula aculeata. On the back are 

 some egg-cases, and on the same tablet a similar group. 1479, 

 2 sp. intertwined with spiral growth ; also a fragment shewing 

 septa. 1480, a sp. on Vitularia salebrosa. On reaching the 

 canal, it has left its mouth, and twisted back at right angles. 

 1481, a specimen on rock, growing upwards, spirally twisted on 

 itself. 1482, a large group off Spondylus, with Petaloconchus, 

 Annelids, &c. 1483, an operculum as found in a fragment of 

 the shell ; also 4 separate opercula, of which 3 are abnormal. 



352 b. ALETES ? CENTIQUADBTJS, var. IMBBICATUS. 



A. t. "A. centiquadro " simili, sed colore intensiore ; rugulis 

 spiralibus parvis, confertissimis, baud decussatis, squamulis 



