4 REPORT — 1856. 



faint, curved, radiating lines indicating the direction in which the spines 

 would normally appear; g, another specimen, smooth over most of the 

 surface, but with spines fully developed at the top ; h, a specimen with 

 wrinkles almost evanescent, yet with a few well-develojied spines, in 

 straight radiating lines ; i, a specimen of normal development, with 

 irregular wrinkles crossed by curved rows of spines ; j, portion of internal 

 margin of specimen h ; k, margin of specimen with spines partly formed, 

 open ; I, ditto fully developed, hollow throughout ; m, profile of specimen 

 beginning with regular margin, smooth, afterwards with irregular margin 

 and a few long spines at one corner; n, profile of smooth specimen 

 beginning regularly, then with difi^erent amounts of irregularity, ending 

 with a regular margin ; o, three specimens in profile, laid for the vertex to 

 coincide ; the first is flattened throughout, forming a regular, obtuse- 

 angled triangle ; the second (shaded) begins very conical, spinous, then 

 with two stages, flattened, smooth ; the third begins like the first, then 

 spreads somewhat, but ends much compressed ; p, an abnormal specimen 

 found by Mr. Cuming in a hole, from deep water, and figured in Trans. Zool. 

 Soc. vol. i. pi. 28. f. 8 ; the long spines are curved backwards over the flat 

 shell, and the cup is extremely prominent ; the dotted line represents the 

 outline of a shell at the opposite extreme, var. compresso-conicum, Proc. 

 Zool. Soc. 1856, p. 167. 



Tig. 4. 'CcEcum undatum, magnified, exhibiting development and variations in shape, 

 sculpture, form of mouth, prominence of plug, &c., observed among about 

 340 specimens. Similar changes in the common Panama species form the 

 CcBcnm diminutum, C. pygmeeum, C. monstrosum, C. eburneum and C.fir- 

 malum of Prof. C. B. Adams : (a, young Cacum, with spiral part attached, 

 species not known ;) b, tube smooth and short ; c, ditto, long ; d, with 

 ■faint indications of rings near the margin ; e, shell more curved ; marginal 

 rings stronger ; /, shell passing at once from smooth to fully ringed state ; 

 ■g, the same, more bent, rings irregular ; h, ditto, curvature irregular ; 

 i, with more rings, outline very irregular ; j, stumpy form, rings close, 

 mouth immature ; k, adult, front view, with multispiral operculum in situ, 

 •apical portion smooth; I, another specimen, mouth contracted, apical 

 portion ringed ; m, nornial state, profile ; n, specimen with rings almost 

 •evanescent ; o, deformed specimen, broken, and mended without rings. 

 All the irregularities in these figures are intended. 



■Fig. 5. Neritina cassiculum. Shy. : a, elevated state, corresponding with subgenus 

 Vitta (Klein) of Messrs. Adams; b, normal state, subgenus Neritina 

 (Swains.) of Messrs. Adams; c, depressed state, answering to restricted 

 genus Nerifella (Humph.) of Messrs. Adams. The same changes of form 

 are observable in the very closely related Neritina picta. Shy. = Fi?^a 

 picta of Messrs. Adams. 



P. P. Carpenter, 



