338 BULLETIN" 11, UNITED STATES NATIONAL MUSEUM. 



the U. S. National Museum are Reval and Gastilizy, in the Echino- 

 spherites limestone (Cl), Baron Toll's estate, in the Kuckers shale 

 (C2) and Jewe limestone (Dl), and at Wesenberg, in the Wesenberg 

 limestone (E). The species also occurs in the Chasmops limestone 

 on the island of Oeland, Sweden. 



Coty pes. —Cat. Nos. 57473, 57476 to 57480, U.S.N.M. 



A fragment of the sectioned type and two thin sections from the 

 Jewe limestone, Baron Toll's estate, and specimens from the Chas- 

 mops limestone, island of Oeland, are in the collections of the British 

 Museum. 



HALLOPORA ? TENmSPtNOSA, new species. 

 Text fig. 213. 



This interesting species, in manner of growth and tabulation has 

 much in common with other species of Hallopora, but differs from all 

 the described forms in the development of rather numerous shallow 

 acanthopores. These are plainly visible at the surface of well 

 preserved specimens, but they are seen in thin sections only when the 

 outermost part of the peripheral zone is cut. 



The zoarium of this species is of dwarfed stems seldom branching 

 more than once. The specimen shown in figure 213 is a typical 

 example of a complete zoarium. The surface is smooth and presents 

 no well-marked maculae, although groups of slightly larger zocecia 

 can be discovered upon close observation. The zooecial apertures 

 are thin walled and vary from a rounded to polygonal shape, accord- 

 ing to the number of intervening mesopores. In the mature condi- 

 tion, three to five small, sharp acanthopores project from each 

 zooecial wall. Four and one-half to five zocecia in 2 mm. 



In vertical sections the tabulation of both sets of tubes is seen to 

 be essentially the same as in the usual species of Hallopora. In the 

 zooecial tubes, diaphragms are abundant in the earliest part of the 

 immature zone, and are then wanting almost entirely throughout the 

 rest of the tubes. In the mesopores, the cross partitions average 

 their own diameter apart. Their place is almost always marked by a 

 constriction of the walls, producing the beaded effect most conspicu- 

 ous in Diplotrypa. 



Tangential sections show thin-walled, rounded to polygonal 

 zooecia with numerous mesopores. Occasionally two zooecia are in 

 contact and then exhibit the dark divisional line of the Integrata. 

 The exceptional feature of such sections is the occurrence of small 

 acanthopores, which, however, are seldom as numerous as at the sur- 

 face itself. These acanthopores are very shallow and, as a rule, are 

 included in thin sections only accidentally. 



This species is referred to Hallopora because of its general zoarial 

 and zooecial structure. The acanthopores and beaded mesopores are 



