W. D. Lang — On Herpetoijora. 5 



placed on the transverse sutures in the suprabranchial groove. For 

 this no function can be suggested, but it is hoped that future work, 

 particularly on recent material, may throw some light on the 

 problems here stated. 



EXPLANATION OF PLATE I. 



The figures have been drawn with the help of photographs, copied by means 

 of an Edinger Projection apparatus. The ambulacral pits and suprabranchial 

 depressions are represented in black for the sake of clearness, but must not 

 be confused with the actual perforations of the test. The figures are not 

 diagrammatic in any other way. 



Fig. 1. Adoral surface of a small specimen of Coenliolectypus serialis from 

 the Seuonian of Algiers (Univ. Coll. , Keading, Geol. Museum, No. F. 284). 

 X c. 6. The ambulacral pits are seen to occur in series conformable to 

 Loven's law, except in area V. The interambulacral depressions are 

 pyriform, pointing adradially. 

 Fig. 2. Part of the adoral region of amb. Ill of Pygaster ' semisulcatus ' , 

 with the adjoining parts of the interambulacra. x c. 6. The ambulacral 

 pits are crescent-shaped depressions (each enclosing a small granule) seen 

 near the peripodium on the lowest member of each triad (except the two 

 proximal ones). The interambulacral depressions are conspicuous, and 

 the granules of the suprabranchial groove are seen to be transversely 

 elongate and arranged in a linear fashion. 

 Fig. 3. Part of the adoral region of amb. I of Discoidea cylindrica, with the 

 adjoining parts of the interambulacra. x 11. The lower part of the 

 figure coincides with the beginning of the peristomial invagination. 

 The ambulacral pits are similar to those of Pygaster, but much smaller 

 in proportion. The suprabranchial depressions are also smaller, and are 

 surrounded by an area devoid of granules. 



II. — Ox Merpetopora, a Xew Genus containing thkee New 

 Species of Cretaceous Cheilostome Polyzoa. 



By W. D. Lang, M.A., F.G.S. 

 (PLATE II.) 



IN a report^ on a visit of the Geologists' Association to the exhibits 

 of Polyzoa and Corals in the Geological Department of tl]e British 

 Museum in February, 1913, the author had occasion to mention two 

 related and unnamed species of nniserial Chalk Polyzoa that hitherto 

 had appeared in records an Jlippofkoa disporsa (von Hagenow), neither 

 of whicli was this species, nor did either belong to the genus Hippo- 

 thoa, Lamouroux.^ Since one of these two forms is very common in 

 the English Chalk and the otlier not rare, it is time for a description 

 of them to be published, that collectors may have distinctive names 

 for them. In addition, a third form that has occurred in England 

 is described, and the rest of the species includeii in the genus are 

 mentioned, so that an idea of the genus as a whole may be formed. 



Hp;epetopora,^ n.gen. 

 Diagnosia. — Incrusting, nniserial, Cheilostome Polyzoa, in wliicli 

 each individual normally lias eitlu-r a distal or one distal and two 



^ Proc. Geol. Assoc, vol. xxiv, pt. iii, pp. 171-2, 191.3. 



' Lamouroux, Exposition Methodique des genres de VOrdre des Polypiers, 

 1821, p. 82. The genotype is the recent Hippothoa divaricata. 

 ■* TO epTTfToV, ' a creeping thing.' 



