116 INTRODUCTION TO CLASSIFICATION. 



This order contains the " Solitary Ascidians," Perophora, 

 and the Botryllidae, Pyrosomidse, and Sdlpidse. 



2. The ABDOMINALIA, in which the branchial sac occupies a 

 comparatively small proportion of the body and lies altogether 

 in front of the intestine and reproductive organs. Clavdina, 

 Amoroucium, and the remaining " Compound Ascidians." 



I formerly proposed a third order the Larvalia to contain 

 Appendicularia, which differs from all the rest in retaining the 

 larval tail as a locomotive organ, and in many other peculiarities. 

 But as, up to this time, all the individuals of this genus which 

 have been discovered have been males, it is possible that the 

 females will turn out to be more complete and of a more ordinary 

 type of structure. 



The BRACHIOPODA. Of these there are two well-marked 

 orders 



1. The ARTICULATA. The valves of the shell are connected 

 along a hinge-line, which is often provided with teeth and sockets. 

 The lobes of the mantle are united upon the dorsal side of the 

 body. The intestine ends in a blind sac. 



The Terebratulidse, Ehynchonellidse, Spiriferidee, and Or- 

 tJiidee, belong to this order. 



2. The INARTICULATA. The valves of the shell are not con- 

 nected along a hinge-line. The lobes of the mantle are completely 

 separated. The intestine terminates in an anus on one side of 

 the body. This order contains the Craniadse, Discinidae, 

 and Lingulidse. 



The POLYZOA are divisible into two orders 



1. The PHYLACTOLOMATA. The lophophore, or tentacu- 

 lated oral disk, is bilaterally symmetrical, and a process the 

 epistome overhangs the mouth. 



The Lophophea and Pedicellinea are comprised in this order- 



2. The GYMNOLCEMATA have no epistome, and the lopho- 

 phore is orbicular. 



This order comprehends the Urnaiellea, Paludicellea, Cy- 

 dostomata, Ctenostomata, and Cheilostomata. 



