296 University of California Publications. [Zoology 



slender tube which has, however, an ovoidal expansion just 

 before it enters the terminal spine (PI. XXVII, Pig. 12). 



This species belongs to the form-cycle of C. pulchra to which 

 species it is evidently closely related. The existence of two c< in- 

 stantly present differential characters in the individuals of this 

 species under my observation leads me, however, to regard it as 

 distinct from C. pulchra. The nearest approach to intergrades 

 appears in one individual of C. pulchra (Pig. 23) in which the 

 second ring is slightly widened. 



The formation of the twisted end of the pedicel in this species 

 may be due to the rotation of the animal during the early period 

 of shell formation. If so, the rotation must be in one direction 

 ■ •(instantly, or at least nearly so, during this period of forma- 

 tion. In locomotion the Tiiitiii in'ilut . in common with other 

 free-swimming eiliates, rotate about the long axis. I have not 

 observed C. pulchra in activity, but in other species which I 

 have seen in motion reversals in the direction of this rotation 

 are not infrequent. It is difficult to find an explanation of the 

 difference between the broad anterior band and the smaller pos- 

 terior ring in C. torta on the supposition made in the case of 

 the rings in G. pulchra, that they are attendant upon the repeti- 

 tion of some phase such as division or conjugation in the life 

 history of the organism. 



The structure of the lorica is similar to that of C. p%lchra 

 with the exception that there are 2-3, and sometimes as many as 

 5 layers of prismatic elements in the rings and collar and that 

 the thickened region of the pedicel is relatively longer. 



The animal has not been seen in normal condition. 



Dimensions. — Total length, 450 /*; diameter of mouth, 65 /t, 

 on rings, 90 /x ; of pedicel, 18-25 /x ; diagonal of pedicel expan- 

 sion, 30 ix ; thickness of wall. 2 to 1/u.; length of terminal spine, 



This species has been taken sparingly in both summer and 

 winter plankton of the Pacific at San Diego, but more abund- 

 antly in vertical than surface catches. It is apparently eupelagic 

 in its distribution. 



