53 



I know, he observes, only the tail of this Asaph, 

 but it is so different from that of other trilobites, that 

 I do not hesitate to establish a particular species, 

 upon the consideration of this part alone. Its gene- 

 ral form is that of a semi-ellipsis; the middle lobe re- 

 presents a very slender cone. The arched ribs of the 

 lateral lobes are perfectly distinct and simple. I can- 

 not perceive in them the slightest appearance of bi- 

 furcation. This sufficiently characterizes the species. 

 But that which further distinguishes it from the 

 others, are the small, elevated points, scattered, and 

 of course rough (serres), with which the skin or epi- 

 dermis is covered, resembling, in this respect, the 

 tail of the Jipus canceriformis. 



This fragment of an Asaph is in a homogeneous, 

 compact, blackish limestone, which contains no 

 other kind of petrifaction. I know not where it was 

 found. It is in the cabinet of M. de Dree. 



On plate 2 of Professor Brongniart's work, he has 

 given figures to illustrate this species; fig. 3 A. re- 

 presents the whole fragment, and 3 B. two of the ribs 

 of the lateral lobes, magnified to show the arrange- 

 ment of the tubercles, which are very peculiar. 



From the above description it will be readily per- 

 ceived, that the A. Hausmanni comes very near to 

 the A. Laticostatus. There are, however, many 

 striking differences, which will be obvious to those 

 who compare our cast with the figures of Brong- 

 niart. The shape of the ribs, and the tubercles upon 

 them; the form of the middle lobe and of the inter- 

 stices between the articulations, are all peculiar to 

 E 2 



