326 EDAVARD S. MORSE ON 



The variation in the size of the peduncle and the mobiUty of the body upon it, is 

 correlated with the greater or less development of the setae. In those forms in which 

 the peduncle is prominent, as in Lingula, or endowed with special muscles, as in Disci- 

 nisca, indicating great freedom of movement, the setae are excessively developed. In 

 D. lamellosa, the setae form a dense fringe about the pallium. As the peduncle becomes 

 more aborted, the setae decrease in length and become less numerous, and finally, when we 

 come to those forms which have no peduncle, and in which the lower shell is appressed 

 or attached to its resting place, as in Crania, Cistella, and Thecidium, the setae are entirely 

 absent. In the young stage of Terebratulina and Hemithyris, where the body has great 

 freedom of movement on the peduncle, the setae are very long, often exceeding the 

 length of the shell. As these forms become larger and have less freedom of motion, the 

 setae become shorter and are less numerous. In forms like Terebratulina, Magellania, 

 and others, where bub slight movement of the body is possible, the setae are not crowded 

 and have no power of motion, nor do we find any muscles to animate such movement as in 

 the Lingididae. The two extremes, then, are the Brachiopoda without peduncles, attached 

 by their ventral shells, setae absent; and the errantian Brachiopoda, e. g. Lingula, peduncle 

 exceeding by several times the length of the shell, capable of vermiform contortions, and 

 setae forming a close fringe about the periphery of the pallium and differentiated into 

 distinct groups, capable of swinging back and forth and having the most complex muscles 

 to effect these movements, as so beautifully depicted by Blochmann (: 01) . 



In Lingula and Glottidia, the peduncle is firmly attached to the ventral shell just 

 within the beak, which, in alcoholic specimens, seems to be embedded in the peduncle. 

 The peduncle issues from the shell as a slender stalk to enlarge immediately to three or 

 four times its diameter at its point of attachment (54: l). The dorsal shell is free, and 

 capable of an extended oscillatory, as well as a fore and aft movement; the posterior 

 occlusor muscle is stretched to right and left as the beak of the dorsal shell swings from 

 side to side. It is difficult to realize the extreme and varied mobility of the peduncle 

 until one has examined Lingulae freshly dug from their burrows. For this reason I feel 

 justified in devoting an entire plate to illustrating the various attitudes assumed by the 

 peduncle of Glottidia in life. 



I have reproduced in 40: 5, a sketch of G. pyramidata which appeared on the cover 

 of my separate on the Systematic Position of the Brachiopoda. This drawing has been 

 repeatedly copied mitil all the character of the original figure has disappeared. For this 

 reason it is here presented. Under Habits, the formation and character of the peduncular 

 sand tubes have been aUuded to. The Lingididae thus far examined agglutinate parti- 

 cles of sand about the posterior end of the peduncle. The perfection of the sand or mud 

 tube varies in the different forms studied. The formation of these tubes, more or less 



