900 Mr. Newport on the Class Myriapoda, Order Chilopoda, 



side, when it will always be found to be a little smaller, — the spines of the 

 reproduced limb are imperfectly developed, are often entirely wanting, and are 

 seldom or ever arranged in their normal regularity. The character derived 

 from the spines must, therefore, be taken in conjunction with others derived 

 from parts that are rarely or ever reproduced ; as, for instance, the dental 

 plates, and also the form of the prse-anal plate, and the lateral appendages, or 

 epimeral plates of the posterior pair of legs. These latter parts occasionally 

 offer good characters ; they are usually consolidated with the coxae, the spines 

 being developed from the epimeral plates. 



The dorsal plates of the segments sometimes afford generic characters. The 

 existence of the stomata, and the emargination of the posterior border pecu- 

 liarly characterize the Cermatiidce, as the alternation of long and short seg- 

 ments with the angles of the latter elongated and pointed do the Lithobiidce. 



The ocelli afford secondary characters of species in Lithobius; since, al- 

 though their number varies at different periods of growth in the same indivi- 

 dual, as first pointed out by Gervais, and confirmed by my own observations, 

 it generally differs in the adult state of different species. When the young 

 Lithobius comes from the egg, it has but a single ocellus on each side of the 

 head, but this is increased to three on each side at its next change. This 

 number is further increased at the subsequent changes, but not until after the 

 animal has acquired its full complement of legs, and then the number is in- 

 creased in a certain ratio at each change of skin. But it does not obtain its 

 full complement until it has very nearly approached its adult size, so that the 

 organs of vision, as in the true Hexapods, are among the last of the external 

 organs that are completed. Even in the adult state the number varies slightly, 

 so that this character cannot be depended on alone, but must be taken in 

 connexion with the number of labial teeth. In the other genera of Chilopoda 

 the number of ocelli is fixed in each genus. 



The number of joints to the antenna is a distinct generic character in 

 Cryptops and Geophilus. It has sometimes been employed, as by Gervais, 

 to assist in indicating the species of Scolopendra, but it is very little to be 

 depended on. In Cryptops and Geophilus the full number is acquired at a 

 very early period; in the latter even soon after leaving the ovum. But this 

 is not the case in Lithobius ; and probably also not in Scolopendra. In Litho- 



