CLASS I 



BRYOZOA 



317 



This is distinguished from the remaining subclass, Phyladolaemata AHman (which 

 includes the freshwater forms), by the complete abortion of the foot, and by the 

 circular arrangement of the tentacles. 



The Mesozoic and Recent marine Gymnolaeniata are almost universally divided 

 into the three orders proposed by Busk : the Cydastomata, Cheilostomata and Cteno- 

 stomata. To these Vine has added a fourth, the Gryptostomata, and Ulrich a fifth, 

 the Trepostomata ; both of which serve mainly for the reception of Paleozoic forms. 



The detailed classification of the Mesozoic and Cenozoic Bryozoa, especially of the 

 Cheilostomata, is less settled than that of the ancient types. This nonconformity is 

 due in part to the widely different views prevailing among authors as to the relative 

 value of the various characters upon which the groups arc founded ; and partly 

 because the mode of growth and zoarial characters in general are much less constant, 

 and, therefore, less reliable than is the case among Paleozoic representatives of the 

 group. 



Subclass 1. GYMNOLAEMATA AUman. 



Order 1. CTENOSTOMATA Busk. 



Zocecia usiudly isolated and developed by budding from the internodes of a distinct 

 tubular stolon or stem. Orifice terminal, with an operculum of setce. Zoarium horny or 

 membranaceous. Marsupia wanting. 



All of the known Paleozoic Gtcnostomata have been described by Ulrich and Bassler in their 

 Revision of the Paleozoic Bryozoa, to which the student is referred for a discussion of these 

 peculiar fossils. Mesozoic and Cenozoic Ctenostomatous Bryozoa are apparently rare and little 

 study has been put upon them. In the Recent seas, the order Ctenostomata is s]>ecifically the 

 least represented group of Bryozoa, although some of the species are quite abundant and 

 widespread. 



i 



Family 1. Rhopalonariidae 



Nickles and Bassler. 



Fusiform segments arranged 

 in a more or less pinnate 

 manner, impressed or almost 

 embedded in the host. 



Rhopalonaria Ulr. (Fig. 

 437, &'). Ordovician to Lower 

 Carboniferous. 



? Terebripora d'Orb. Ter- 

 tiary and Recent. 



Family 2. Vinellidae 

 Ulrich and Bassler. 



Creeping base of zoarium 

 of simple or locally jointed, 

 delicate, tubular threads ar- 



<3 



Fio. 437. 



--"-—> A, Allonemafusiforme (N. and E.t, 6/1. B, C, Vinella repens Ulr., 2/.j 



ranned either imthout order or and is/j. d, AscodictyonsteUaUm(-s.?,nA-E.^,vii, e, A.p^^^^^^ 



,Kvivj^K<j and B., 6/1. F, /MeroHema «?j)i7toce U. and B., 6/1. G, Bhopulonana 



proceeding from more or less te,m("s U. and B., e/i (after ulrich and Bassler). 



definitely marked centres. In- 

 ternodes ivith a single roio of pores or, in one genus, closely punctate ; zocecia unknown. 



Vinella Ulrich (Fig. 437, B, G). Zoarium of very slender parasitic tubular threads 



