Vol. 69.] DERIVED CEPHALOPODA OF THE HOLDERNESS DRIFT. 173 



Coroniceras rotiforme, although entered as doubtful in Yorkshire 

 lists, is probably present in several varieties : for many fragments 

 have been seen, and Mr. Morfitt possesses a fine example. These 

 fragments are in a shale which is similar in character to that 

 containing the angulatce. 



Coroniceras sauzeanum (d'Orb.) and JEtomoceras scipionianum 

 (d'Orb.), in spite of not having been found in place since Tate & 

 Blake's time, are really abundant as excellent casts in a certain 

 very hard dark limestone, of which large, somewhat rectangular 

 boulders are frequently secured, well filled with representatives of 

 these species in various stages of growth. 



A glance at the appended list (p. 180) will show many names 

 of the genus Coroniceras new to the Yorkshire lists. The same 

 is also true of the Arnioceras group. 



Coroniceras trigonatum has been well described by A. Hyatt l ; but 

 his figured types of the species are rather remote from our speci- 

 men, which possesses a very massive body -whorl of acutely sagittate 

 section. The grooves shown in the figures are absent from along- 

 side the sharp keel of the Drift example. We have now seen on the 

 coast fragments of four more examples of this bulky ammonite, 

 although it does not appear to be represented in the museums, 



Arietites tumeri (Sow.), or some near ally, is not infrequent as 

 fragments, but we have not been able to secure a cabinet specimen, 

 not even a fairly complete one. It will be at once called to mind 

 that Sowerby founded this species on a Drift specimen from 

 Norfolk. 



Arietites brooli Eeynes has occurred more frequently, and con- 

 sequently some good examples were obtained. 



The so-called ' Arnioceras semicostatum ' is so abundant in its 

 various forms that it might be styled ' the Ammonite of the Drift.' 

 It chiefly occurs by the hundred, in cubical blocks of the hard dark 

 limestone so well known in English museums. Although these are 

 always labelled 'from liobin Hood's Bay,' it is suggested that they 

 were really obtained by collectors from Drift material, since neither 

 I nor any one whom I have ever met has found this limestone in 

 place, although it has been much sought for. Again, the museum 

 blocks can easily be matched along the Holderness shore to-day. 



Some specimens of this ammonite are found in a shaly matrix ; 

 but then they are not so well preserved. The first time that I 

 visited Withernsea for collecting-purposes, there was a really 

 wonderful display of this fossil. There had been a storm associated 

 with a spring-tide, as is very usual on that coast, and apparently 

 a big mass of shaly material had been washed up and scattered, for 

 the beach was literally paved with semicostatum slabs for quite 

 100 yards. Such a display has never been seen since. 



The large ammonites of the zone are generally found as mere 

 fragments ; yet some excellent examples have been secured by 

 other collectors, and are now housed in the local museums. 



1 'Genesis of the Arietidse' Mem. Mas. Cotnp. Zool. Harvard, vol. xvi 

 (1887-89) No. 3, p. 182 & pi. vi, fig. 3 ; pi. vii, fig. 1 ; pi. xii, fig. 15. 



