230 J- Platpaib Mc Mureich, 



3. Gyrostonia incertuni n. sp, 



Talcahuano. 1 specimen. 



Tumbes near Talcahuano. 6 specimens. 

 No. 448 a. Puerto Montt. 1 specimen. 



The form assumed by this species in contraction difers con- 

 siderably in different individuals. Some are distinctly barrel-shaped, 

 smaller both at the margin and base than at the middle (Fig. 10), 

 while others are more elongated (Fig. 11) and more cylindrical, 

 although still showing a diminution in diameter toward either ex- 

 tremity. 



The base was evidently adherent, though probably but feebly so ; 

 the column was almost sraooth, except for transverse wrinkles due 

 to contraction. In many specimens the tentacles were completely 

 concealed, while in others they were more or less exposed and were 

 Short, conical and acuminate, and more or less distinctly brownish 

 in colour. Their number seemed to be somewhat irregulär; four 

 cycles are regularly present and in serial sections through the 

 uppermost part of the column of an individual from Tumbes I found 

 representatives of a fifth cycle over some of the exocoels. Accurate 

 counts were not easy to make, owing to the greater or less con- 

 traction of all the specimens, but in one individual eighty were 

 counted, in what was approximately a quadrant of the large indi- 

 vidual from Talcahuano there seemed to be representatives of six 

 cycles, while in one of the specimens referred to below, in which 

 about half the tentacles were lacking, I counted fifty-seven re- 

 maining. 



A peculiarity observed in several of the specimens from Tumbes 

 was the absence of tentacles from a considerable portion of the disc. 

 The individual sliown in Fig. 11, if viewed from the opposite side 

 has the appearance represented in Fig. 15, no tentacles being per- 

 ceptible in almost one-half of the circumference of the disc, the 

 ridged stomatodaeum passing directly over into a very narrow and 

 smooth disc and this into the column wall. A similar condition was 

 observed in two otlier individuals, but the remainder were normal. 

 The condition seems to be more probably the result of injury than 

 a normal suppression of the tentacles, but it possesses some interest 

 in connection with Lesson's description of Äcfinia picta. 



On account of the differences in shape there is considerable 

 Variation in the size of the various specimens. The largest barrel- 



