ON THE DEVELOPMENT OF LINGTTLA ANATINA. 



71 



I. Muscles. 



Since the parietal muscle layer has been described in connec- 

 tion with the body walls (p. 47), it will not be necessary to 

 touch here upon this structure, and the muscles found in the 

 arm-apparatus and the peduncle will, for reasons of convenience, 

 be dealt with in later sections. I shall, therefore, in the present 

 confine myself to a description of the shell-muscles. 



The muscles of Brachiopods bear different names according 

 to different authors. Among them I shall follow throughout the 

 present paper the terminology of Blochmann ('oo). The follow- 

 ing table will be found necessary to avoid confusion : — 



Before entering into the description of the particular muscles 

 I shall describe here the finer structure of a muscle, taking as a 

 representative the occlusor posterior in a larva of the 9 p. c. stage 

 (PI. VIL, Fig. 117). The muscle is non-striated and consists of 

 rigid looking'fibres. The nuclei which are scattered here and there 



1. It is worth noting that Blochmann in his " Untersuchmegan ü. d. Bau d. Brachio- 

 poden 2 ler Theil " ('00) describes the posterior adjuster of Hancock as the 31. obliquus médius 

 in the text (p. 107 1 , while throughout his atlas (e.g. Tafel XV., 21.) the 31. obi. med. is 

 jnarked with the abbreviation obi. int. and vice lersd. 



