438 



Genus Meioceras*. 



Testa adolescens solute spiralis, haud planata ; adulta scepe in- 

 jiata. Apertura obliqua. Operculum spirale, extus concavum; 

 anfractibus linea spirali instructis. 



Ceecum, pars, Stimpson. (Pars= Infiatulum, B. M. Maz. Cat. 

 p. 314, note*.) 



The young shells of this group might easily be passed over as Ver- 

 metidce ; when perfect, however, the minute plug displays their 

 Ceecous origin, while their peculiar growth, in a loose spiral instead 

 of a plane, seems to warrant their separation. The young and adult 

 shells have been found together (1) fossilized in the coral rocks of 

 Barbadoesf, (2) in recent shell sand from the W. Indies, and (3) 

 in the coarse sponge of commerce. The peculiarities of the adult 

 form are easily explicable from its spiral origin. If the decollated 

 parts had remained, Meioceras would bear a loose resemblance to 

 Helicoceras, and Ceecum to Toxoceras. It is presumed that these 

 creatures are more stationary in their habits than Cceca ; their mode 

 of growth would enable them to keep pace with sponge, but would 

 be inconvenient in crawling through the narrow passages in which 

 Cceca have been found. All the species found are glossy, without 

 sculpture, and with a texture often partly opake, partly transparent, 

 in irregular concentric bands interrupted by longitudinal ribs, like 

 the framework of inflated fashionable dress. The adult shells can 

 scarcely be distinguished from Fartula, the irregularity of outline 

 being the best criterion. 



39. Meioceras nitidum, Bean, MS. 



M. t. nitidissima, vitrea seu subcornea, subdiaphana ; fusca, sen 

 albida et Candida nebulosa ; adolescente anfractibus paucis, 

 rapide augentibus ; t. adulta valde gibbosa, plerumque maxime 

 infiata, utraque extremitate constricta ; apertura valde declivi, 

 circiter angulum 1 30° planum apicis respiciente ; margine an- 

 tico maxime arcuato, postico subplanato : septo submucronato, 

 conico, marginibus laterali et dorsali rectis, apice parum ele- 

 vato, acutiore, dorsali : operculo parum concavo, linea spirali 

 extante instructo ; anfractibus paucis, circiter v. 



Variat t. magis elongata, minus infiata. 



* /jie'iov, rather small; icepas, horn. 



t Not from Grignon, as erroneously stated in the note, p. 314 of the ' Mazatlan 

 Catalogue.' Those who posseas the work are requested to cancel the note alto- 

 gether. The very faulty name Infiatulum was simply intended as a section under 

 Ceecum, founded on the shape only. As the peculiar shape is found to vary even 

 in the species, and as the true generic character is in the C'ornucopice-sbaped 

 growth of the adolescent shell, I gladly adopt the excellent name given at my re- 

 quest by Mr. H. Adams. The finding of the fossil specimens was due to the 

 skilful labour of the late Mary Clow, the faithful attendant of S. Worsley, Esq., 

 long known as (though blind) the zealous investigator of the Inferior Oolite fossils 

 of Dundry. It was to serve as eyes to guide his knowledge, that I commenced 

 the study of shells. 



