64 i?. T. Hill — Goniolina in the Texas Cretaceous. 



can hardly be said that they favor any one face, for they often 

 divide the O faces into trangles. Other striations occur less 

 abundantly which may be referred to the intersection of planes 

 of coO with O, seeming to indicate a minor parting. Stria- 

 tions parallel with the edges of O, have been previously noted 

 2. by Cathrein (Zwillingsbildung am Mag- 



netit, Zeitschr. f. Kryst. xii, 47, 1887), 

 and again by Miigge (ISTeues Jahrb., 

 1889, i, 244), by whom they were re- 

 garded as polysynthetic twinning on the 

 spinel law, and due to gliding planes. 

 Such twinnings and striations on spinels 

 proper, .have been long known (see 

 Striiver, Zeit. f. Kryst., ii, 480) and are 

 noted in most of the mineralogies. On 

 Cathrein's crystals the striations seem 

 especially to favor one face, and this adds weight to the above 

 explanations. The striations on the Lake Cham plain crystals 

 are not especially parallel to any one face, but cross each other 

 frequently, and the other striations parallel to ocO, add some 

 complexity. The beds which contain them have been subjected 

 to great dynamic movements and these partings are very prob- 

 ably due to pressure — which has also developed the fine pseudo- 

 cleavage planes in the massive mineral. If it were allowable 

 to conceive of a chief parting along O, and a rarer one along 

 ocO, occasioned by such pressure, without any accompanying 

 twinning, 1 should think it more likely to be the true cause of 

 the phenomena. The massive mineral shows these octahedral 

 parting planes quite as large as the hand. 

 Geol. Laboratory, Cornell University. 



Art. VI. — Occurrence of Ooniolina in the Comanche Series 

 of the Texas Cretaceous ; by Robert T. Hill. 



For several years I have been puzzled by a peculiar organ- 

 ism which occurs abundantly in the basal and medial beds of 

 the Comanche series of the Texas Cretaceous. This organism is 

 preserved in chalky beds of whose lithologic character it par- 

 takes, and is about the size and shape of ordinary playing mar- 

 bles used by boys except that it is slightly elongated, and 

 flattened at one end where there is a circular depression re- 

 sembling the point of attachment between a fruit and its stem. 

 The surface is minutely pitted or reticulated. 



Possessing no library facilities at Austin, I recently sent 

 suites of these fossils to various paleontological friends in the 



