BRACmOPODA. 489 



the origins of the cardinales muscles. I have proposed the name of 

 "capsularis," for the sum of the cameo-tendinous fibres which have 

 the attachment in question.* In conjunction with the completely 

 encircling fibres of the peduncular capsule, they must compress and 

 elongate the peduncle. 



In addition to the muscles arranged in the more or less definite 

 masses above described, there must be enumerated the fibres 

 which are lodged in the walls of the canal (Jig. 186, m) travers- 

 ing the stems of the fringed arms ; and the muscular fibres of the 

 pallial lobes, which latter are extremely feebly developed, and recog- 

 nisable only near the periphery. Thus, to recapitulate the designa- 

 tions of the several muscles in the Terebratula, as demonstrated by 

 dissections of the Ter. chilensis, Ter. psittacea, and Ter. JlarescenSy 

 there may be enumerated the — 



Adductor longiis anticuSy 



Adductor longus posticus^ 



Adductor breris, 



Cardinalis, 



Retractor superior, 



Retractor inferior, 



Capsularis, 



Brachial inuscleSy 



Pallial jnuscles. 

 The first seven muscles leave more or less recognisahle impres- 

 sions on the interior of the valves: the marginal muscles of the 

 mantle are too feehly developed to mark the shell, as it is impressed 

 in the Lamellibranchiate bivalves. 



In the Lingula the homologue of the adductor brevis is situated at 

 the peduncular end of the shell ; it is very short and thick, and 

 passes from one valve to the other. The adductor longus posticus 

 arises from by a common origin on one side and by two origins on 

 the other side of the visceral mass, behind the middle of the sliell. 

 They pass obliquely to the opposite valve, the single muscle gliding 

 between the fasciculi of the divided one."|" Each adductor longus 

 anticus arises single from the ventral valve, near the fore part of the 

 visceral mass, and divides as it passes obliquely to the dorsal valve, 

 the divisions decussating, but being inserted close together. The 

 arrangements of these powerful adductors are such as to effect sliding 

 movements of the valves on each other, besides closing the shell, and 

 to compress and variously affect the interposed viscera and visceral 

 lacunae with their contained sinuses. The long pedicle of the Lin- 



* CCCIII. t CCC. pL vi. fig. 13. 



