78 L. A. BORRADAILE. 



Internally the pyloric division presents the usual filtering apparatus of valves and fringes with- 

 out any remarkable features. Of the terminal valves the dorsal and lateral are much elon- 

 gated and pointed. 



It will perhaps be of interest here to indicate the bearing of the gastric armature 

 just described on the systematic position of the genus\ The following characters belong 

 especially to the fore-gut of the Pagurinea : — (i) The long, narrow shape of the stomach, 

 (ii) The slight inclination of the pyloric region, (iii) The form of the mesocardiac ossicle. 

 (iv) The longitudinal direction of the dorsal edge of the zygocardiac ossicle, (v) The elon- 

 gation of the cardiac side plates, (vi) The almost horizontal direction of the pennate and 

 inferolateral cardiac ossicles. 



Within the Pagurinea, the following characters separate the Coenobitidae - from the 

 Paguridae : (i) The lower edge of the cardiac disk has its hairs arranged in tufts on 

 pointed projections of the body of the disk, (ii) The lateral tooth has no notch on its 

 lower edge, (iii) The median tooth carries transverse ridges, (iv) The exopyloric ossicles 

 have a strong saddle-shaped curvature, (v) The pyloric ossicle is expanded and strengthened 

 at its anterior angles. 



The differences which separate Coenobita from Birgus are small, but the following may 

 be mentioned:— (i) The anterior tubercle of the lateral tooth is wanting in Coenobita. (ii) The 

 hinder edge of the mesocardiac ossicle is rather more convex than in Birgus. (iii) The 

 anterior edge of the cross-piece of the prepyloric ossicle is more concave, (iv) The calcified 

 ring round the opening of the invagination on which the post-oesophageal brush is borne, 

 articulates, in Birgus, with an elongated triangular strip in front of the pennate ossicle, 

 (v) In Birgus, the cardiac disk and the arrangement of hairs on its lower edge are more 

 developed than in Coenobita, and form the " suboesophageal valves" of Mocquard^ 



The gastric musculature shows no important difference from that of the Pagurids as 

 figured and described by Mocquard. The strong gastric mill is provided with a correspond- 

 ii^g'y powerful set of muscles to work it. The anterior gastric muscles are a pair of stout 

 strands inserted on the mesocai'diac ossicle and diverging slightly as they run forward 

 thence to their origin from the under side of a low, rounded, transverse ridge of the carapace, 

 situated above the bases of the antennae and eye-stalks. This ridge is the " procephalic 

 apophysis." The posterior gastric muscle of each side is divided into two bundles — an 

 inner one, inserted on the thickened plate at the outer end of the pyloric ossicle, and an 

 outer one, somewhat broader than the inner, inserted on the exopyloric ossicle. The origin 

 of the inner bundle is partly from the anterior side of a thin, flat, triangular apophysis, 

 which projects inwards and somewhat forwards from the cervical groove a short distance 

 from the middle line, and partly from the carapace in front of this apophysis*. The outer 

 bundle arises in front, and a little to the outside, of the other. The cardiopyloric or 

 su.perior cardiac muscles consist on each side of three bands running backwards from the 

 hind edge of the mesocardiac to be attached to the exopyloric ossicle. Of these three, 



' For the facts on which the following paragraph is based * Such an apophysis seems, from Mocquard's remarks on 



I am indebted to Mocquard (op. cit.). the gastric musculature of Pagurus, to be wanting in that 



^ The family Coenobitidae includes the genera Coenobita genus. It is however present in Eupayurus bernhardus, 



and Birgus. where it is directed /orward*. 



3 Ann. Sci. Nat., (6), xiii. 3 (1883). 



