Miscellaneous. 16.) 



nature of the cephalic appendages which surround the mouth in a 

 manner characteristic of the group. 



The class Podostoraata may be defined as a group of marine 

 Arthropods in which the cephalic (Limulus) or cephalothoracic 

 (Trilobites) appendages are in the form of legs, i. e. ambulatory 

 appendages, usually ending in forceps or larger claws (chelae), 

 which in the sole living representative of the class are arranged 

 in an incomplete circle around the mouth : the basal joint of each 

 leg is spiny, so as to aid in the retention and partial mastication of 

 the food. No functional antennae, mandibles, or maxillae. Eyes 

 both compound and simple. Eespiration by branchiae attached to 

 the abdominal appendages, which are broad and lamellate in Mero- 

 etomata, and cylindrical, with narrow gills, in Trilobita. The brain 

 supplying nerves to the eyes alone ; the nerves to the cephalic or 

 cephalothoracic appendages originating from an oesophageal ring ; 

 the ventral cord ensheathed by a ventral arterial system more per- 

 fectly developed than in insects or scorpions. Coxal glands highly 

 developed, with no external opening in the adult. The class 

 differs from the Arachnida, among other characters, in having no 

 functional cheliceres (" mandibles") or pedipalps ("maxillae"); in 

 the cephalic appendages either ending in larger claws or forceps, or 

 in being simple, the terminal joint not bearing a pair of minute 

 claws or ungues like those of Arachnida and Insecta, enabling their 

 possessors to climb as well as walk. Podostomata have no urinary 

 tubes. Limulus undergoes a slight metamorphosis, while in Trilo- 

 bites the adult differs from the larva in having a greater number of 

 thoracic segments. 



From the Crustacea the Podostomata differ in the lack of func- 

 tional antennae and mouth-parts, in the compound eyes having no 

 rods or cones, in the brain innervating the eyes (compound and 

 simple) alone, in the shape of the head and pygidium or abdominal 

 shield, and in the arterial coat completely enveloping the central 

 nervous cord. 



The Podostomata are divided into two orders : — ■ 



1 Xiphosura. 

 I. Merostomata, with three suborders : < Synxiphosura. 



II. Trilobita, 



Eurypterida. 



On the Anatumy and Classification of the Phytopti. 

 By Dr. Alfred Nalepa. 



The cephalothorax of the Gall-mites is unusually reduced, the 

 abdomen, on the contrary, considerably extended and annulated. 

 Besides the organs of the mouth the former bears only two distinctly 

 quinquearticulate pairs of legs. The mouth-organs have the form 

 of a more or less strongly bent rostrum. The stilettiform chelicerae 

 lie in a sucking-tube formed by the maxillae, which is supported by 

 the labium. The maxillary palpi are four-jointed, only the basal 

 joint is amalgamated with the maxilla. At the extremity of the 

 abdomen on each side of the anus there are two semilunar rctrac- 



