g4 EXPÉDITION ANTARCTIQUE BELGE 



is much less in Hornera lichenoides, and is not estimated to exceed ten. Ostroumoff (') says 

 the larvae of Hornera are the largest of the marine Ectoproct Bryozoa, with which he is 

 acquainted, measuring o.48 mm : in size downwards he sa} T s, are Hornera, Tubulipora, Frondipora, 

 Lichenopora, Crisia, which last are only o.7 mm . 



The H. antarctiea belongs to the Hornera lichenoides group, and at first I named it 

 H. ranwsa ÀlacG. ( 2 ), as it agrées with that species in its slender form, and in the way in which 

 the branches arise often at right angles, but it differs from that species in not having the zoœcia 

 enclosed in rhomboidal spaces, and the large « punctations or vacuoles » are wanting. In 

 H. lichenoides there are a few large pits or « punctations » instead of the moderate sized pores, 

 and there is a large semilunar pit, placed distally above the zoœcial tube, with iarger pits by 

 the border of the zoœcium. The ridges passing at each side of the zoœcia, and forming the 

 rhomboidal spaces, are not very marked in H. lichenoides whereas in H . frondiculata they are very 

 pronounced, and further there is a large opening some little distance above the projecting 

 zoœcial tube. In H. frondiculata, the zoœcial tube is wanting on the distal part ; and onlv 

 projects on the proximal, that is to say a deep notch is eut away on the upper part, whereas in 

 other mentioned Hornerœ the tube is entire, and we certainly seem to hâve at least three closely 

 allied but distinct species. Figures of typical H. frondiculata Lamx. from the Mediterranean 

 and of H. lichenoides L. from Franz Josef Land are given for comparison, as many of the 

 published figures do not give the characteristic minute structure. The growing ends of Hornera 

 antarctiea (fig. \ï) hâve a smooth surface with small pores, and then they look like Entalophora, 

 until subséquent growth forms the pits and rugose structure. The dorsal wall of Hornera is 

 thick forming what has been called in fossils an epitheca, but it is in no way différent in 

 structure from the thinner walls, and has similar pore tubes through it. 



I cannot agrée with MacGillivray in thinking that H . frondiculata ought possibly to be 

 referred to H. lichenoides. However, a spécimen from Naples is much like the H. lichenoides, 

 having similar dorsal ovicells, and at first it was named lichenoides, but 1 propose to separate 

 it as mediterranea, though it may be the H . serrata of Meneghini, a name however previously 

 employed by Reuss. It has the zoœcia irregularly placed, the outer zoœcia are much the 

 longest, the inner ones are not much raised, and the border is entire, the zoarial growth is 

 similar to that pf H. lichenoides, the diameter of the interior of the zoœcial tube is about o.i2 mm , 

 being somewhat Iarger than in lichenoides or antarctiea, in both of which the tubes are internally 

 about o.i mm . 



The Hornera verrucosa Reuss from the Septarienthon is ver}' similar to H. antarctiea. 



Hornera occurs, fairly abundantly, in the tertiary beds of Europe and Australia, it occurs 

 also in the Cretaceous often called Reteporidea &c. It has been recognised that the Paleozoic 

 Thainniscus closely resembles Hornera, and it is difficult to see upon what grounds such a species 

 as T. ramulosa Ulrich (•') can be separated from Hornera. According to Ulrich Thainniscus 

 commences in the Niagara, with one species, followed by two in the lower Helderberg, then 

 continues through the various Devonian and Carboniferous groups, culminating in the Permian. 



(i) Zur Entwickelungsgeschichte der Cyclostomen Seebryozoen, p. 1S0. [MM. Zool. Stat. su Neapel, vol. VII.) 



(2) Description of New or Little Known Polyzoa, pt. XII. [Tratts. Roy. Soc. Vict., 1886, p. 3, pi. I, fig. 4.) 



(3) Ulrich Paleontology of Illinois «Bryozoa». (Geological Survey of Illinois, vol. VIII, p. 610, pi. LXII, 

 figs. 4-46.) 



