22 Hill Paleontology of the Trinity Division. 



The Serpulas have such wide geologic range and-so lew specific 

 characters that they are of little value in geologic diagnosis. 



Occurs at gypsum bluffs of the Little Missouri, and in great 

 abundance at. the plant bed near Glen Rose, and also throughout 

 the extent of the lower fossiliferous Glen Rose beds in Texas. 



MOLLUSCOIDEA. 



Genus indeterminate. 



Microscopic oval cells about one millimeter in length, growing 

 in colonies attached to shell ofSerpula paltixiensis and other forms ; 

 cells not overlapping, but in close contact with each other, form- 

 ing a single layer of delicate net-work. 



The cells of this species have not the pyriform shape or im- 

 bricated arrangement of Membranipora or the vibracular cells of 

 Lunulites, and hence are assigned to no generic position at pres- 

 ent. This form is the only one belonging to this order yet found 

 in these beds. It occurs attached to other shells in the beds of 

 the plant locality on the Paluxy near Glen Rose, Texas, at the 

 base of the Glen Rose beds. 



MOLLUSCA. 



Anomia texana sp. nov. 

 Plate I, Fig. 5. 



Anomia sp. indet. Hill. Arkansas Geological Survey, Annual 

 Report 1888, vol. n, p. 135. 



Thin, discoidal, indistinguishable specifically from many spe- 

 cies of this genus; right or lower valve attached, concentrically 

 laminated; left upper valve arched and very irregular; seldom 

 exceeds one-half inch in greatest diameter. 



This species abounds in the earliest fossiliferous horizon of 

 the Trinity Division, such as the beds in Paluxy creek, west of 

 Glen Rose, and at the gypsum bluffs of the Little Missouri, in 

 Pike county, Arkansas. It also occurs in most of the localities 

 throughout the extent of- the Glen Rose beds, 



