Part II - State of New Jersey

142 CRETACEOUS FOSSILSBelen~nites onterican~cs JIorton! 1831, Synopsis, Cretaceous Group, pl.I: figs. 1-2.Relenrnitella anlnrii,asn \Vhitficl(l, 1892, pl. 47, figs. 4-7.Belenr.nitella a~~~ericann \Yeller, 1907, pl. 109, figs. 1-2.Bolelnnitella amerieana Gartlner, 191.6, pl. 12, figs. 4-6.Rele~~lnitella a~~tericolzcr Groot, Organist and Richards, 1954, pl. 7,fig. 1.Introduction.-Belentnitclla alnerica~la (3Iort.) var. a~noricnna nor.var. is morphologically intermediate between the estre~ne varieties ofthe species described belom.It is also hy far the 111ost common variety of B. amerieana (Morton)s. I. in almost ill1 fossil lots of the species studied by the writer fromNew Jersey, Delaware, and Maryland. Therefore B. anlericana var.amevicana may appropriately be eonsiclered as typical of the species,all the more so as thc above discnssed leetotype of R. a~aericana s. I. isits typical representative.Morphology: Guard generally large, this variety including nearlyall the largest specin~ens of 1). a,n~erica?ra s. I. known to the writer. Inits proportions the guard fluctuates from long an11 n~odcrately sturdyto short and stout. The extremes known to the writer are reproducedon pl. 77, fig. 2a-2b; pl. 78, fig. 4a-411: 111. 79,. figs. la-lb, 6a-6c. Inthe majority of the specimens studie[l the guaril in (.he lateral aspecttapers gradually and evenly all thc may from its alvcolar edge to apoint some 10-30 mm. above its apical end. From this point the taperingincreases more or less strongly, mith its second increase often occurringjust hefore the apical end of the guard (see pl. 76, fig. la,Id; pl. 77, fig. 2b). These increases in tapering produce more or lessvide or narrow but alvays more or less rounded and obtuse apiealends mith or without a clearly defined mucro. Somewhat more rarelythe guard tapers at the same or almost the same rate to its very end,nVhieh thus becomes very narrow, long and acute (see pl. 79, figs.la-lc) and mostly but feebly mucronate. In other rare instances theguard does not perceptibly taper apically over the anterior third or halfof its length, remaining virtually subcylindrieal throughout this section,(see p1.79, figs. 2,3a, 6a-6c). In such instances, howt:ver, the guardnearly always tapers more or less pronouncedly over its posterior halfor two-thirds.In the rentral aspect the guard is mostly subcylindrical to feeblyconical from its alveolar edge to a point 25-50 mm. above its apieal end.Below the said point thc tapering toward the apical end of the guardincreases markedly producing a more or less rounded and obtuse end ofthe guaril with or ~vithout a clearly defined mucro (see pl. 76, figs. la,lc; pl. 77, figs. 2a-c ; pl. 78, fig. +a). In the remaining minority of specimens,however, the vcntral outline of the guard raries from a markedlyconical shape with or ~x.itliout ;L strongly rounded apical end and well(lefined mucro to somewhat li~necolate shape with a fairly olituse andNEW JERSEY GEOLOGICAL SURVEY