W. D. Lang — The Reptant Eleid Polyzoa. 61 



This table shows that the Eleid ' genera ' fall into two groups, 

 those with avicularia and those without them. The former series 

 has no term corresponding with Elea in the other series, that is, no 

 erect foliate 'genus.' Both series are wanting in the more primitive 

 types of zoarium, those that are encrusting and consist of zooecia 

 arranged either in single series or two or three abreast. 



I. The Determination of Species and the Morphology op 



THE Z0(E0IUM. 



The individuals (zooecia) of an Eleid colony, exclusive of gonoecia 

 and of gonocysts, may be of three kinds — 



1. Normal zooecia. 



2. Avicularia. 



3. Closed zooecia. 



In half the 'genera' avicularia are absent. Closed zooecia only 

 differ from normal zooecia in the possession of a calcareous covering 

 to the apertures. Therefore, it is only by means of the normal 

 zooecia that the specific characters of the whole family can be 

 brought into line. For this purpose the characters of the aperture 

 appear most useful on account of their variety and the ease with 

 which they can be seen. The shape of the zooecia, the character 

 of their boundaries, and the frequency or rarity of the apertures 

 vary so much in a single zoarium that they are of little use as 

 specific indices. In one species at least, Semimultelea acupiinctata 

 (Novak), the character of the punctation of the front wall is used. 

 Consideration of this character in the Jurassic forms of Stomatopora 

 has led the author to consider that it is of little practical use in 

 specific determination, because it is only clearly shown under 

 favourable conditions of preservation or of subsequent weathering.^ 



In some species the distal end of the zooecium in the neighbourhood 

 of the aperture is on the general level of the surrounding zooecia. 

 Such zooecia are described as immersed. When the distal parts of 

 the zooecium rise above the general level of the surrounding zooecia 

 the zooecium is said to be emergent. 



The apertures in the various species differ in their actual size, the 

 relation of their diameter to that of the zooecia, their sbaj)e, and the 

 nature of their border. In any given zoarium the shape of the 

 apertures will vary considerably ; for instance, from triangular with 

 rounded angles to circular. Therefore, in determining a species, the 

 shape of the majority of apertures must be taken, and if this is done 

 the use of the table below should not prove difficult. 



A triangular shape of aperture may be taken as morphologically 

 typical of the family. This triangle may be equilateral ; or isosceles 

 with a small distal angle (Fig. 11) ; or the equilateral triangle may 



1 W. D. Lang: "Jurassic Forms of the 'genera' Stomatopora and Prohoseina,^'' 

 Geol. Mag., 1904, p. 318 ; and " Stomatopora antiqua, Hainie, and its related 

 Liassic Forms," Geol. Mag., 1905, ^. 258. 



