4:2 i Geological Society. 



femora, tibiae and tarsi, and the middle tibiae (except at 

 the apex) testaceous, "Wings clear hyaline, the costa and 

 nervures black ; the stigma fuscous in the middle, a faint 

 fuscous cloud occupies the basal three fourths and the whole 

 of the second and third cubital cellules; the first recurrent 

 nervure is received very shortly before the middle, the second 

 in the basal fourth. Abdomen priiinosc, the base and 

 sides of the petiole rufo-, the base of the second segment 

 yellowish, testaceous ; the sides of the basal and the whole 

 of the second ventral segments yellowish testaceous. 



[To be continued.] 



PROCEEDINGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 



December 21st, 1904.— J. E. Marr, Sc.D., F.R.S., 

 President, in the Chair. 



The following communication was read : — 



' On Certain Genera and Species of Lvtoceratidae.' 

 By S. S. Buckman, F.G.S". 



This paj)er deals with certain specimens sent by Mr. Beeby 

 Thompson from the Northampton Sands, one of which is remarkable 

 for its homoeomorphy with Phijlloceras. In order to classify the series 

 of Toarcian-Aaleuian Lytoceratidte to which these species belong 

 (jurense and allied groups), it is necessary to note that there is 

 evidence of a definite sequence of phylogenetic 8ta<j:es. In orna- 

 ment there is, at first, elaboration; but, later, simplification from a 

 costate to a smooth stage. In whorl-shape there is a tendency to 

 pass from the primitive evolute to the involute whorl, the nrabihcus 

 constantly contracting. Parallel with this there is a further 

 tendency to pass from stout to more compressed whorls. While 

 the Lytoceratidse have a more primitive whorl-shape than the 

 Phylloceratida2, their lobe-line is more advanced ; and hence, while 

 the advance of the former produces a certain external homoeomorphy 

 with the latter, the more advanced lobe-line remains a feature of 

 distinction. The successive stages of development maybe indicated 

 in terms of species, thus : (1) Gtrmalni, (2) torulosiim, (3) annulose 

 species not yet named, (4) jtireuse, and (5) phAlloeeratoidan. Four 

 new genera are described, and two new species ; three new names 

 are proposed, and one generic name revised. 



