260 J- Pi^AYFAiR Mc Murrich, 



The base is adlierent and, in tlie majority of tlie specimens, 

 tlie limbus is somewhat recurved, presumeably the result of con- 

 traction subseqnent to the removal of tlie specimens from the sub- 

 stratum to which they were attached. The coliimn wall is covered 

 throughout its entire extent Avith closely set tubercles, for which 

 110 definite arrangement in rows can, as a rule, be discerned, though 

 in one specinien from Cavancha (No. 18) such an ari-angement could 

 be made out distinctly in the upper part of the column but not 

 lower down. The general indistinctness of the arrangenient is due, 

 however, to the large nuinber of rows which occur and also to the 

 fact that the majority of the tubercles are Compound, consisting of 

 a hollow Stern bearing at its sumniit two, three, or four hemispherical 

 knobs. Simple tubercles, with but a siugle knob also occur but they 

 are much less frequent than the Compound ones, and since all the 

 tubercles are formed by evaginations of the column wall in the 

 intermesenterial Spaces, they must i-eally be arranged in longitudinal 

 rows. 



The surfaces of the knobs may either be quite smooth or may 

 be marked with fine lines. In the specimens from Cavancha a 

 peculiar condition was observed, in that the extremities of the pedicles, 

 instead of being rounded and knobbed, were elongated and more or 

 less curved, so that the column had the appearance shown in Fig. 38. 

 The individuals presenting this peculiarity resembled the forms with 

 knobbed tubercles (Fig. 37) in other respects, however, and theie 

 seems to be no reason for regarding them as forming a differeut 

 species. 



The Upper portion of the column, especially in the more elongated 

 individuals, is strongly inverted, the tentacles and margin being 

 concealed; but in the lower and broader individuals the incurving 

 is not sufficient to conceal the parts mentioned and it may he seen 

 that the margin is provided with acrorhagi which are lobed and 

 of a different color than the column. A distinct fosse occurs be- 

 tween the acrorhagi and the bases of the tentacles. These are 

 arranged in about flve cycles and are probably about 192 in nuinber 

 in the smaller individuals and 384 in the largest. A slight difference 

 in their shape, no doubt due to diflferences in contraction can be 

 noticed in different individuals, in some they are distinctly acuminate,. 

 while in others they are obtusely pointed. A dark spot, indicating 

 the presence pf a Perforation is distinct in the centre of the apex 

 of niany tentacles, and in some cases mesenterial filaments protruded 



