450 MK. S. S. BTJCKMAN ON [Aug. I906, 



(1) Analogous Stages among some Terebratuloids. 



Glossothyridoid Stag e. — Notable representatives of this stage 

 of development may be seen in Glossothyns nucleata and G. hijopopus, 

 in Pseudoglossothyris curvifrons and others ; in Aulacothyris spp. 

 var. ; in Orthotoma. Some specimens of G. nucleata and of Aulaco- 

 thyris Haasi, S. Buckm., show the commencement of the next 

 stage. 



Plicated Glossothyridoid Stage (T. Euthy mi-stage). — A 

 species which attains to the beginning of this stage is Pseudoglosso- 

 thyris galeiformis (M'Coy) ; and one of the stocks of the so-called 

 Aulacothyris which attains this stage is made a genus, Antipty china, 

 Zittel. Then Dictyothyris coarctata shows the full development of 

 the stage — allusion is only made to its shape, not to its ornament. 



Bifidate and Perforate Stages. — Outside the diphyoids 

 there seems to be no development quite analogous to these. There 

 is a checking of growth in the median lobe and a protrusion of the 

 side-lobes, making bilobate forms, and this is, of course, a commence- 

 ment of the bifidate stage. But further than that there seems to be 

 no development. Of this bifidate stage, Zeilleria spp. var. may be 

 cited as examples, and perhaps Z. cornuta as a notable case. The 

 stage may also be noted in Cincta, and in a few Terebratulae, my 

 T. imitator, for example. This bilobate character is generallv 

 regarded as one of the special generic features of Zeilleria, so that 

 the bilobate long-looped Terebratuloids are called by that generic 

 name. But this is only a stage of development at which independent 

 long-looped stocks arrive. Zeilleria, like Aulacothyris, is polygenetic ; 

 and to obtain a true classification on genetic lines, it is necessary 

 to recognize that at present these genera only indicate the stages 

 of development — the Glossothyridoid and the Bilobate — of many 

 different stocks. To distinguish between these stocks other characters 

 will have to be taken into account. 



Imperforate Stage. — Of other Terebratuloids in this stage 

 there is no evidence, because there is none of their having come 

 through a perforate stage ; but attention may be directed to a form 

 curiously like Antinomia pileus : it is termed ' Waldheimia bilobata, 

 Stoppani ' by Zittel [40] ; and it has even the reflected anterior 

 margin — the beginning of a sulcate stage as shown in A. pileus. 

 1 Waldheimia bilobata, Stoppani ' is from the Upper Lias of Luera, 

 Lombardy. 



(2) Successive Development of similar Ammonites. 



I desire to draw attention to a case of successive independent 

 development of like forms among Ammonites — first, because it 

 parallels the development among the diphyoids ; secondly, because 

 the nomenclature-history is instructive. I refer to the Jurassic 

 Ammonites with knotted keel. There are two groups of these — a 

 Middle Lias (Pliensbachian) and Oxfordian. The Pliensbachian 

 group is in two series — the Ammonites-margaritatus set succeeded 

 by the A. spinatus forms. The Oxfordian group appears at three 



