EAKLY PALEOZOIC BRYOZOA OF THE BALTIC PROVINCES. 



257 



This species is most closely related to Orhipora solida, agreeing with 

 it in all characters save the larger size and fewer number of its 

 acanthopores and its much smaller zoarium. A glance at figures 148 

 and 149 will indicate that in spite of their similar characters, the 

 tangential section of each is quite distinct. The associated Orhipora 



Fig. 149.— Oebifora acanxhophoea. a, the type-specimen, natural size; b, tangentul section, 



X20, ILLUSTRATING THE IBREGULAB ZOCECIA AND NUMEROUS LARGE ACANTHOPORES; C, SEVERAL ZOCECIA 

 OF THE SAME SECTION, X20, SHADED TO BRING OUT THE CLEAR TISSUE OF THE ACANTHOPORES AND THE 

 AMALGAMATED WALL STRUCTURE MORE PIAINLY; d, VERTICAL SECTION, X20, WITH STRUCTURE OF WAIJS 

 AND ACANTHOPORES. LOWER ASAPHUS LIMESTONE, HALLt>DDEN, ISLAND OF OELAND. 



indenta has much smaller zooecia, thinner walls, and smaller acantho- 

 pores projecting far into the zooecial cavity. 



Occurrence. — Rare in the lower Asaphus limestone at Halludden, 

 island of Oeland, Baltic Sea. 



The type-specimen and figured tliin sections are in the collections 

 of the British Museum. 



ORBIPORA INDENTA, new species. 

 Text fig. 150. 



On account of the deep indentation of the zooecial cavity by nu- 

 merous small acanthopores, a zoarium of this species often gives the 

 impression of a septate coral like Tetradium. Thin sections, how- 

 ever, show that the minute structure is precisely as in the other 

 species here referred to Orhipora. 



The zoarium of the type-specimen is a small, elongate, dome-shaped 

 mass, 14 mm. in height and 9 mm. wide, with the usual epithecated 

 flattened base. The surface is smooth and without perceptible 



