6 PA TTEN AND REDENBA UGH. [Vol. XVI. 



communicates with the intestine. The intestine begins a short 

 distance in front of the plastron and proceeds straight back- 

 ward, close to the haemal side of the plastron. The oesophag- 

 eal collar surrounds the entrance to the oesophagus, and lies 

 entirely on the neural side of the plastron. The ventral cord 

 passes posteriorly along the same side. 



The plastron itself is roughly rectangular, with the long axis 

 parallel to the long axis of the animal. It is produced anteriorly 

 into two stout processes (anterior cornua, a.c, PI. I, Figs, i and 

 2), posteriorly into a cleft median process (posterior process, 

 p.pr.^ Figs. 1-4) and a pair of short bars (capsuliginous bars, 

 cap.b., Figs. 1-4). 



Laterally, near the anterior margin, are two pairs of long rod- 

 like tendons (lateral cornua, I.e., Figs, i and 2), and near the 

 posterior border is a pair of short stout processes (latero-poste- 

 rior processes, l.p.pr., Figs. 1-4). 



Neurally a pair of processes arise from near the bases of the 

 latero-posterior processes, pass around the ventral cord, and 

 unite on the neural side of it to form the occipital ring {oc.r.y 

 Figs. I, 3, and 4). This ring is connected posteriorly with the 

 capsuliginous bars (cap.b.). 



Haemally a pair of short stout processes (dorsal or haemal 

 processes, h.pi'., Fig. 2) arise midway along the lateral margins 

 of the plastron. 



The body of the plastron is a thick plate of fibroid cartilage, 

 flat or slightly concave on the neural side, with the lateral mar- 

 gins (in.r., Figs, i and 3) sharply elevated, particularly towards 

 the anterior end. The haemal side is concave in transverse 

 section. The lateral edges are much thickened anteriorly, and 

 produced beyond the body of the plastron to form the anterior 

 cornua. 



2. The anterior cornua {a.c, Figs, i and 2) are a pair of 

 stout transversely flattened processes. To each process are 

 attached three muscles, which go to the haemal side of the 

 carapace ; one directly forward from the extremity, one perpen- 

 dicularly from the inner surface of the process, and one obliquely 

 forward from the haemal margin. 



The neural margins of the processes and the entire lateral 



