Cretaceous and Tertiary Cirrt pedes. 20.'5 



will sulUce liere to say that in the nnnibei' of valves of the 

 capitulum it agrees with Pollicipes, but differs iu the more 

 ereet and ScnlpellumAWa sliape of the capitulum, in the size 

 and position of the upper latera, and iu the specialized form 

 of the scuta, characters seen in the more specialized forms of 

 Scafpc//iun. In fact, it is a Pollicipes, which, while retaininj; 

 the large number of capitular valves, is developing some 

 of the characters of a Scalpellum. It probably represents 

 an early attempt at that specialization in the form and 

 })Osition of the upper valves which was subsequently acquired 

 independently by the more specialized forms o{ Scalpellum. 



There now remain to be considered the s[)ecies grouped in 

 the genus Calantica. This genus was evidently derived from 

 a d'ollicipes-Wke form, and the valves still retain their 

 Follicipes-Y\ke character, in consequence of which the fossil 

 forms have been referred mainly to Pollicipes. Calantica 

 differs from Pollicipes in the greater specialization of the 

 capitular valves, and the capitulum is composed of only 

 scuta, terga, and a carina, with but a single basal whorl of 

 valves, the valve which is homologous with the upper latus 

 in other forms being still a member of the lower whorl. 

 There are two groups of recent species, namely, an Oriental 

 group (Calafitica, s. str.) and a North Atlantic-Mediter- 

 ranean group [ScillcBlepas) . These two groups may con- 

 ceivably I'cpresent two collateral stocks, but at present I am 

 inclined to think that the species included iu Calantica, s. str., 

 are derived from the more primitive Scillcelepas, mainly 

 through the weak calcification of the basal whorl of valves, 

 Scillculepas is known from the Pliocene and Miocene of 

 Sicily and Italy respectively, and in the present paper has 

 been shown to have existed iu the Upper Seuonian and 

 Danian, but no fossil has yet been proved to belong to the 

 more typical species of Calantica, s, str. The probability is 

 that the ancestral forms of Seillielepas occurred in the 

 Jurassic, but although at present there is not sufficient 

 evidence to prove this, it is certain that some of the dis- 

 connected valves found in Jurassic rocks have much resem- 

 blance to those of Scillcelepas. It is fairly evident that iu 

 Scillalepas we have a group of species intermediate between 

 I^ollicipes and Scalpellum, and therefore it is another example 

 of the many forms that have been derived from a Pollicipes- 

 like ancestor through the specialization iu the number and 

 position of the capitular valves. 



The recently-described Titanulepas *, although ranked as 



* 1913, T. H. Withers, True. Zool. Sue. Loudou, p. 943. 



