310 Prof. M. Schultze on the Genus Cornuspira, and on 



of the spire of the larger Polythalamia (and, indeed, belonging 

 to different genera according to Ehrenberg), must resemble a 

 Cornuspira. As is stated in the passage above quoted of my 

 book on the Polythalamia, the two species of the genus in 

 question described by me occur with as many as six to seven 

 whorls. They are Planorbis-like shells, without any division 

 into chambers in the interior. Now, are there any chambered 

 Rhizopod-shells, Polythalamia, of which the centre is such a 

 Cornuspira ? This Ehrenberg had to prove ; at least, he ought 

 to have adduced a single well-ascertained case of the kind, if he 

 wished to combat successfully against the validity of the genus 

 Cornuspira. Ehrenberg has adduced none, and could not ad- 

 duce any ; for, in fact, there are no Polythalamia with such a 

 shell. This Ehrenberg knows as well as I do, and it must con- 

 sequently be doubtful whether his assertions are only to be 

 called " incautious.^^ 



But as regards the young Agathistegia (i.e. Mi/zoZi</«), already 

 compared by myself with young Cornuspira, Ehrenberg's mode 

 of bringing these in to get rid of the genus Cornuspira is posi- 

 tively absurd. I am already accustomed to Ehrenberg's citing 

 my book on the Polythalamia only when he attacks it, but not 

 mentioning my name when his investigations furnish a con- 

 firmation of mine. Once already I have protested against this 

 proceeding, at the same time publishing some examples of it*. 



My statements upon the development of the Miliolidce {Agathi- 

 stegia, D'Orb.) are so complete and definite, that any possibility 

 of confounding the young with Cornuspirce after they have at- 

 tained a certain age is prevented. In their earliest youth they 

 are very similar, but as soon as more than a single complete 

 whorl is formed, characteristic differences make their appearance. 

 In the Miliolida at this age, the first or even the second divi- 

 sion of the chambers shows itself; and the number of these 

 divisions now increases by one with every half whorl, so that 

 Miliolida with six to seven whorls already consist of twelve or 

 more chambers. Cornuspira with the same number of whorls, 

 on the contrary (and this is the distinguishing character), have 

 not the smallest indication of partitions; nor do they acquire 

 them with a still larger number of whorls, as appears from the 

 Cornuspira cretacea described by Reuss from the Westphalian 

 chalk, in which from ten to fifteen whorls have been counted. 



From this, we see upon what j-irinciples Ehrenberg suppresses 

 genera : somewhat as if the couchologist were to include the 

 shells of Planorbis and Spirula in one genus on account of the 

 similarity of their winding — or as if any one were to unite all the 

 Entomostraca, of which the young cannot be distinguished from 

 * MuUer's Archiv, 1856, p. 167. 



