320 0ARU0N1FKR0U8 FORMATIONS AND FAUNAS OF COLORADO. 



that it would lie (Icparting from tlieii' obvious relationsliips to discriminate them by 

 more than specific ranlc. 



ScA'eral ycai's ago 1 described under Syrriif/ojxira" two species tliat present cer- 

 tain close resemblance to some forms for which Grabau about tiie same time projjosed 

 the generic name Ceratopora. Structui'ally my species seem to belong to Grabau's 

 genus, but they differ in their mode of growth in the same manner that Syrinqopora 

 does fi'om Aulo2wra and the erect forms tentative!}- referred to Moiv'dipm'a do from 

 the t_vpical ones. The parallelism in growth shown by these species is significant, 

 and seems to me to indicate that this character should be gi\'en onlj^ secondary 

 importance. 1 am not sure but that mj- original reference of those species was 

 correct. Strangely enough, Grabau does not discuss the relationship of his Cera- 

 tojwra with either AulojMra or Syringopora. Yet this relationship seems to me ^'ery 

 real. Nicholson placed MoniUpora in the Auloporida3, but Grabau erected for it 

 and Ceratopora a new family which he called the Moniliporida3. This seems to me 

 altogether superfluous. 



On a slide from the Crested Butte region (station 2290) prepared for the micro- 

 scopic studj^ of the form referred to Chsetetes mille2yoraceus, two j^oung Aulopora- 

 like colonies are shown which probably belong to the form described above from 

 more abundant material. In one case the youthful colony had been completely cov- 

 ered over and probably inclosed by the Ohsetetes upon whose massive corallum it had 

 started to grow. The other was a later and apparently more prosperous attempt to 

 colonize upon the same Chisteten. Both incidents are transcribed upon the same thin 

 section. The individual corallites in this instance are about 2 mm. in diameter and 

 appear to be without septa, septal spines, or tabulse. The walls are so much thick- 

 ened as to leave an insignificant aperture in the center, the wall substance being 

 radially fibrous. 



Associated with the auloporoid at both localities are numerous minute bodies, 

 some of which resemble spicules so closely as to suggest that they may be of organic 

 origin. They maj-, however, be only segregations of calcite (of which substance 

 they now consist) without organic beginnings. The largest probabl}' does not exceed 

 1 mm. in length. The shape is irregularh^ elongate with one end usually larger than 

 the other, and with the length some four or five times the greatest breadth. In 

 other words, the outline is straight and tapering, with one end bluntlj' and irregu- 

 larly rounded, and the other more or less pointed, but it is interrupted b}" sjiinous 

 projections of considerable size, so that these bodies pi'esent an almost endless variety 

 of shapes, and it is extremeh' difficult to frame a generalized description of them. 

 They can scarcely be considered echinoid spines even if the^^ are organic at all, and 

 the general appearance is rather that of Om'gonia spicules. If the organic nature of 



nU. S. Geol. Surv., Mon., Tol. 32, pt. 2, 1S99, pp. 507, 510. 



