366 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XV 111. 



and Prawns possess. They render Palinurus an ugly customer to 

 attack and an uncomfortable mouthful to swallow. 



About the middle of the dorsal surface we find a transverse cer- 

 vical groove which runs downwards and forwards on each side of the 

 carapace. 



This groove (Latin cervix, neck) marks the junction of the head 

 with the thorax and is the only evidence of segmentation in the 

 carapace. 



Behind the transverse portion of the groove is a quadrilateral space 

 known as the cardiac area because the heart lies below it. The 

 grooves that mark its lateral limits are continuous in front with the 

 cervical and are also continued backward to form two longitudinal 

 grooves, known as the branvluo- cardiac grooves, because all the 

 descending portion of the carapace below these grooves forms a 

 cover tor the branchial or gills and hence is known as the gill-cover 

 or in Greek, bravchiostegite. 



This cover is homologous with the pleura of the abdominal 

 somites. 



The sterna of the cephalo-thorax are much more obvious in Pali- 

 nurus than in the Cray-fish, Lobster or Prawn. Between the five pair 

 of walking legs is seen a large triangular or shield-shaped plastron, 

 with its apex pointing forward. A number ot transverse sutures show 

 it is formed of the five sterna united together. On separating the foot 

 jaws their three sterna are seen as a rod continuous with the apex of 

 the plastron, a stout tubercle marking the points of union between its 

 segments. 



The epimera of the thoracic segments form the inner wall of the 

 gill chamber as a continuous delicate layer which at the dorsal limit 

 of the chamber is continuous with the inner lining of the gill- 

 cover. 



The wall formed by the epimera is thin and but slightly calcified 

 except just above the articulation of the appendages. Above the last 

 walking leg it forms a specially strong plate bearing a stout process 

 in shape and function resembling a shirt stud. The posterior margin 

 of the carapace is tucked or reflected inwards and on each side of this 

 reflection is an oval buttonhole into which the top of the epimeral 

 stud buttons. 



