100 ORTHALICINJE. 



The form of the cusps of the central and inner lateral teeth varies 

 within several of the genera, which are based almost wholly upon 

 characters of the shell. In Oxyetyla, Liyiius and Ort/idl/'rits there are 

 species with the median teeth lance-shaped and others with them 

 blunt. It is not possible to divide the series in any rational manner, 

 using this character as a basis. 



The fundamental color-pattern consists of five spiral bands (gener- 

 allv reduced to three) and numerous longitudinal stripes. The modi- 

 fications of pattern are further discussed under the several genera. 



In the subdivision of the Orthalicina into genera, there has been 

 wide divergence of opinion ; but few who have occasion to study ex- 

 tensive series will dissent from the view that the fundamental division 

 of the group cannot be based upon the lanceolate or obtuse form of 

 the median teeth, nor upon the truncate or continuous condition of 

 the columella, nor upon the simplicity or thickening of the outer lip. 

 These characters all intergrade imperceptibly, sometimes even within 

 the limits of one single species. A far more stable feature is found 

 in the sculpture of the nepionic shell ; and I would divide the sub- 

 family primarily into (1) forms with the ante-natal shell pitted like 

 a thimble, and (~2) those in which it is smooth or slightly wrinkled 

 longitudinally. The senior name for (he first .-cries of specie.- is 

 Ortlt<ili<-iis of lleck, ]s;>7. That for the second series is Llymis of 

 .Mnntfort, 1810. 



These two groups are easily of generic rank ; but when further 

 subdivision into genera is attempted, it i.- obvious that \\ e are dealing 

 with groups of less systematic value than the genera of linliiiuilliiiP 

 reeogni/ed in this work. The usage of mo-t cmichologists in recent 

 vears, however, ha- been to recogni/e two or three genera within the 

 group with -month early whorls; and keeping in mind the fact that 

 their differences are not of much >ignilicance, it may lie he-l to adopt 

 -nine further division. I would, therefore, arrange the genera and 

 subgeiiera ihus : 

 I. Marly whorls pilled, ORTHALICU8, witli the subgeniis Jfr/nr- 



thalicuf. 

 II. Karlv \\horls -mooth or nearly so, 



1. 1 1. 1 i .-. \\ith siibgenera ('i>rt>'i and ffemibulimus. 

 Ox Y 8 T T L A. 

 l'"i;rin I;H! \rni . 



Or, to .-how more clearlv the true rank and relationship of the 

 group.-. : 



