iv INFERIOR OOLITE AMMONITES. 



mantle. 1 In the former case the specimen is septituberculate ; in the latter 

 non- septituberculate, or, more simply, tuberculate. 



Ornamentation. — The greater or less elaboration of the ornament (costee and 

 tubercles) upon the conch may be stated in the following terms : crassornate, 

 ornate, subomate ; when there is no ornament, Isevigate. 



Begulari- and Trregulari-omate. — The ornament is irregular if it varies 

 considerably in size, or is not uniform in its development. When the irregularity 

 consists merely of occasional variation in size, a more particular term may be 

 insequi-ornate. Similar qualifying terms may be used in connection with the 

 particular details of the ornament. 



Periphery. — In order to describe all the different aspects of the periphery an 

 elaborate scheme of nomenclature would be required. That would be out of 

 place here, but the following terms are necessary. 



The periphery may be planate, convex, or concave ; when the concavity is rather 

 restricted the periphery is sulcate ; if furnished with a carina it may be carinati- 

 convex or carinati-sidcate ; 2 when somewhat like the roof of a house sloping into a 

 more or less definite edge, it is fastigate. Its sloping sides may be slightly convex, 

 flat (truly fastigate), or slightly concave, when the following modificatory definitions 

 are necessary : convexi-, plani-, and concavi-fastigate. A narrow flat periphery is 

 tabulate; divided by a carina it is carinati-tabulate, which is perhaps better than 

 bitabulate. 



Carina. — The different developments of the peripheral carina may be distin- 

 guished as alticarina, carina, parvicarina. The carina is sometimes partitioned 

 off by a septum, when it has been called a hollow carina (vide p. 81) ; when not 

 so parted it has been designated a solid carina. The terms are not exact, and 

 may be replaced by septicarina and non- septicarina. In most cases an alticarina 

 is a septicarina, but not always, — for instance, Hi/perlioceras. 



The umbilicus requires many technical terms, but the following may suffice for 

 the present. 



Gradumbilicate. — A portion of each inner whorl is exposed, making the 

 umbilicus in the form of steps, or like an amphitheatre. 



Concavumbilicate. — A small bowl-shaped umbilicus, so noticeable in the 

 Ammonites concavus, Sow. The lower edge of the inner margin of the over- 

 lapping whorl is superposed on the upper edge of its predecessor, and as the 

 inner margin has more or less of a slope, the result is in some cases a regularly 

 concave umbilicus like a small bowl. When the superposition is not quite exact, 



1 In Sonninia, in Stepheoceras (- Slephanoceras, i.e. Humphriesianum group), <fcc. : when the 

 test is lost the core is still tuberculate. 



2 Formerly carinate-bisulcate, but it is really one furrow divided by a carina. 



