L 65 ] 



articulated as Terehratula, Spirifei; Rhynchonella, the latter com- 

 prised species with non-articulated valves as Lingula discina, Sm. 

 Some very important modifications in the animal were connected 

 with these two divisions, especially in what related to the muscular 

 system. According to Morse, the Brachiopod were reproduced by 

 ej^gs, -generally kidney-shaped and irregular, which were dischai-ged 

 from the anterior margin of the shell, and dropped just beyond the 

 pallial mciubrane, hanging in clusters from the setce. Some 

 uncertainty had prevailed as to whether there was a male and 

 female individual ; Lacage-Duthiers and Morse stated that the sexes 

 were separate and described them as such in Thccidium and Tere- 

 bratulina, and the French zoologist went so far as to suggest that 

 a difference was even observable in the shell. Professor Morse 

 described the embi-yo of TercirafttZwo. with great minuteness during 

 its six stages of development. It was divided into two, three, or 

 four lobes clothed with vibratile cilia ; and before becoming 

 attached, swam or whirled head foremost by means of vibratile 

 cilia which covered the body. 



MANTLE. 

 Both valves were lined by the delicate membrane, termed the 

 " pallium," or mantle ; it secreted the shell, and was generally 

 fringed with hoi-ny bristles, or setce. The mantle was composed of 

 an outer and inner layer, between which were situated blood 

 channels or lacunes. These arterial trunks and veins constitute the 

 vascular system. On certain parts of the surface of the mantle 

 occurred a vast number of microscopic, flattened, calcareous, 

 denticulated plates, or spicule, destined, no doubt, to stiffen the 

 portions that contained them. The digestive oi'gans, viscera, as well 

 as the muscles, took up only a small place in the contiguity of the 

 beak, and were separated from the general cavity by a strong 

 membrane, in the centre of which the mouth is located. The nervous 

 system consisted of a principal ganglion, of no great size. 



BEACHIAL APPENDAGES. 



He must next briefly describe those beautiful and singular 

 organs, eminently characteristic of the Brachiopoda, termed arms, 

 or more correctly lah'uil, on account of each member being a 

 prolongation of the lateral portion of the lips or margin of the 

 mouth ; the lamellibranchs, or conchifera, had analagous 



