1896. SOME NEW BOOKS. 335 



Jullien made a " tribus inovicellata ''' for the Aetidae, but a paper 

 is now in the hands of the Linnean Society figuring the ovicells. 



In the Microporidas there are a large number of species with 

 external ovicells, while many are without ; but is Gregory right in 

 placing Onychocella in this family ? The genus Onychocella is a 

 very interesting one, occurring in great abundance in the Chalk,, 

 continuing abundant through the Tertiaries, with only one or two 

 representatives now living. The form described by Gregory as 0. 

 jiabellifonnis, Lamx., very closely resembles several Chalk species, but 

 revision of these is much wanted, as the number of synonyms is known 

 to be very great. We may, however, hope to see this genus brought 

 into order when the catalogue of the Cretaceous Bryozoa is published. 



In Micropova the oral aperture corresponds with the operculum, 

 but this is not the case in either Membranipova or Onychocella. In 

 the living Onychocella angulosa the opesial opening is large, while the 

 operculum is but small, and is entirely attached to the membranous 

 wall. Further, there are no external ovicells, and the ova pass into a 

 membranous chamber at the distal end of the zooecium, near to the 

 basal wall. In recent species of Onychocella there are trabeculae border- 

 ing the operculum as in Cellaria, and an interesting Cretaceous fossil 

 called Eschavella argtts, d'Orb., has teeth in the aperture like Cellaria, and 

 has avicularia of the type known in Onychocella, while the ovicells are 

 like those of Cellaria. In the fossil Onychocella an external ovicell is 

 rare, though in Onychocella lamarckii there is a slight elevation where 

 the "oberhohle" of Hagenow occur ; and Jullien speaks of the ovicell 

 of the Onychocellidse being raised, but in none of the species described 

 by him is there any ovicell. In a number of forms such as Eschara 

 dichotoma, Hagenow, it is very difficult to decide whether the opening 

 is opesial, or was closed by the operculum. 



To return to Dr. Gregory, he accepts Ulrich's order Trepto- 

 stomata, which contains the families Ceramoporidae, Heterotrypidae, 

 and Amplexoporidae, represented in the Jurassic by Ceriopora, Chilopova, 

 and Heteropora, but the Heteropora of Blainville is somewhat limited. 



The Cyclostomata are divided into four suborders, the Articulata, 

 Tubulata, Dactylethrata, and Cancellata. " Dactyleihrae " is the name 

 proposed for a form of " aborted zocecia " consisting of short caecal 

 tubes closed externally, but whether this is, as Gregory considers, a 

 structure of classificatory value, may at present be considered an 

 open question ; however, much of the usefulness of such a work is 

 that questions are raised which lead to further investigation. The 

 best critic of classification is time, but many groupings which have 

 not stood this test have yet been useful in helping towards an orderly 

 arrangement of our knowledge. 



Since the genus Meliceritites included species with well developed 

 avicularia, and others distinctly cyclostomatous, Gregory has placed 

 the latter in a genus Haplocecia. 



This catalogue, clearly placing before us what is known con- 

 cerning the Bryozoa of the Jurassic period, will be warmly welcomed 

 by those who are working at this or kindred subjects, and will be a 

 standard work of reference. A. W. W. 



The Literature of the Pleistocene in Ireland. 

 A Bibliography of Irish Glacial and Post-Glacial Geology. By R. Lloyd 



Praeger. Being an Appendix (no. 6 of vol. ii.) to the Proceedings of the Belfast 



Naturalists' Field Club for 1895-96. Pp. 239-316. 8vo. 

 The literature referring to the Glacial and Post-Glacial geology of 

 Ireland is somewhat scattered, and many valuable papers occur in 



