125 



The ZoANTHARiA BUGOSA have a simple or compound 

 corallum, composed of a septal apparatus derived from four 

 primary elements, instead of six as in the preceding groups. 

 The septa are incomplete, but never porous, and the visceral 

 chamber is filled from the bottom by a series of transverse 

 tabulae, or by a vesicular structure which often constitutes the 

 principal part of the Polypary. 



The ZoANTHAEiA TTJBTTLOSA havo a simple or compound 

 eorallum with imperforate walls ; the septa, columella, and 

 tabidae are absent from the visceral chamber, and some feeble 

 striae are only visible. They form a single family, the Auliporidoe. 



The ZoANTHARiA CATTLictrLATA have a dendroidal skeleton or 

 sclerobase for supporting the Polypi, as in many Alcyonia, 

 Gorgonia, and Isis. Its surface is smooth or spinulous, and not 

 sulcated as in Alcyonaria. 



2nd OrcZer.— ALCYONAEIA. 



The Alcyonaria have a somewhat exceptional history : one 

 singular family referred to this order, the Grraptohthidse, 

 appertain to the Lower Silurian rocks, to which they are 

 special. No other family of this division is found between that 

 epoch and the White Chalk, where they are sparsely distributed. 

 Alcyonaria continue to increase in numbers and genera through 

 the Tertiary epoch, and attained their greatest development in 

 our present seas. 



The sclerenchymatous Zoantharia are divided into the 

 following six sub-orders : — 



Ist Sub-Order. — The Zoantharia apoeosa — are characterized 

 by posessing a eorallum composed essentially of lamellar dermic 

 sclerenchyma, with the septal apparatus highly developed, 

 completely lamellar, destitute of pores, and consisting of six 

 elements, and no tabulae. The foHaceous or lamellar structure 

 of the calcified tissue, which furnishes one of the principal 

 characters of these Corals, is always recognisable in the 

 external part of the septa. This order includes four famiUes: 

 Tfrbinolid^, Oculinid^, Astreid^, and Fungid^. These 



K2 



