xiii PHYLUM CHORDATA 23 



This sub-order contains only one family, the Doliolidce, with the 

 three genera, Doliolum, Anchinia, and Dolchinia. 



Suh-Order h. — Hemimyaria. 



Thaliacea with a more or less fusiform body, with sub-terminal 

 oral and atrial apertures. The muscular fibres are arranged in 

 bands which do not form complete rings. There is no tailed larval 

 stage. 



This sub-order is probably best looked upon as comprising only 

 one family, the SalpidoR. 



Suh-Order c. — Pyrosomata. 



Thaliacea which reproduce by budding, so as to give rise to 

 hollow cylindrical colonies, open at one or both ends, having the 

 zooids embedded in the gelatinous wall in such a manner that the 

 oral apertures open on the outer, the atrial on the inner surface 

 of the cylinder. There is no tailed larval stage. 



This sub-order comprises only one family the Pyrosomidce, with 

 • one genus, Pyrosoma. 



Order 3.— Ascidiacea. 



Mostly fixed Tunicata, either simple or forming colonies by a 

 process of budding, and, in the adult condition, never provided 

 with a tail. The test is a permanent structure, usually of 

 considerable thickness. The muscular fibres of the mantle (body- 

 wall) are not arranged in annular bands. The pharynx is large, 

 and its walls are perforated by numerous stigmata leading into a 

 surrounding atrium or peribranchial cavity, which communicates 

 with the exterior by an atrial aperture. Many form colonies by 

 a process of budding ; and most undergo a metamorphosis, the larva 

 being provided with a caudal appendage, supported by a notochord 

 similar to that of the Larvacea. 



Suh-Order a. — Ascidice simplices. 



Ascidians in which, when colonies are formed, the zooids are not 

 embedded in a common gelatinous mass, but possess distinct tests 

 of their own. They are nearly always permanently fixed and 

 never free-swimming. 



Including all the larger Ascidians or Sea-Squirts. 



Suh-Order h. — Ascidice compositce. 



Fixed Ascidians which form colonies of zooids, embedded in a 

 common gelatinous material without separate tests. 



This order includes Botryllus, Amarmcium, Diazona, and a 

 number of other genera. 



