Echinoid Jaw-fragments. 129 
cular genus to which any or all of these fragments may have belonged would have 
no sure basis. It has nevertheless seemed advisable to give figures and descriptions 
of these fragments, as materials towards some eventual history of the evolution of 
this wonderful mechanism. Of course by Triassic times the early stages had long 
been passed; indeed a well-developed lantern existed already in the Silurian Palaco- 
discus and Echinocystis. But between those early forms and the lantern of a recent 
Echinus there is considerable difference; there are even differences between them 
and the recent Cidaris. A detailed comparative study of this kind of fossil remains 
might well prove as valuable as the account of recent forms contained in Lovén’s 
«Echinologica». (Bihang K. Svenska Vet.-Akad. Handl. XVIII, Afd. IV, No. 1, 
July, 1892.) 
Note on Terminology. — It may not be out of place to urge upon those who 
may contribute towards such a study the desirability of using a precise and accepted 
terminology. The confusion of terms introduced by some recent writers (who unfortunately 
speak as men having authority and not as the scribblers) is hard to explain or to excuse, 
considering how large is the choice of valid terms.* 
The skeletal constituents of the lantern, in order beginning at the oral centre, are: — 
Five interradial Teeth each ending in an aboral plume (sometimes called matriz.). 
Each tooth is borne by a Pyramid, a paired structure of which the right and left halves 
are known as Hemi-pyramids or half-pyramids, and sometimes as jaws (Wiefer, 
machoire), a term better avoided since it has also been applied by some writers to the 
whole pyramid and by others to the adoral portion of the hemi-pyramid. For each hemi- 
pyramid consists of an adoral and an adapical element. The ten adoral elements were 
described by J. T. Kirin (1784, p. 42) as «ossicula falciformia. . . . ex quibus maxillae, 
vel, si mauis, dentes molares quinque duplicati componuntur», and in the next sentence 
he speaks of the «paria maxillarum». The term Maxilla, previously used by RONDELET 
(1554, De Piscibus, lib. XVIII, cap. 30) for the same structures, is highly appropriate and 
is here adopted; it corresponds to the piéce mazillaire of F. Brrnarp (Paléontologie, 
1893) and the Kinnlade of Jon, MULLER (1854). Between the maxillae «intra duo ossicula» 
says KLEIN (loc. cit.) «dens caninus, velut in alueolo latitat». Alveolus then, here as 
elsewhere in anatomy, means a cavity in which a tooth (or other object) is lodged. T. H. 
Stewart (1861) seems to have been the first to misapply this term to the maxillae them- 
selves; but his example should not be followed. The maxillae are united, «arcte conjuncta» 
(KLEIN) by a Symphysis. The small aboral element of each hemi-pyramid is called the 
Epiphysis, a term apparently due to Jon. MULLER (1854), and adopted by T. H. 
Stewart and Loven among others, while A. AGassiz (1874, Revision, p. 688) prefers 
apophysis. Each pyramid then consists of two maxillae and two epiphyses. The epiphyses 
may unite interradially to form the Arcus (arch, Knochenbogen, arc-boutant). Whereas 
the separate epiphyses of Clypeaslter were observed by A. Parra (Descripcion de diferentes 
piezas de historia natural, &c.) so early as 1787, the arcus of an Echinid was figured 
(Tab. XXXI, fig. @ and 7) and described (p. 42) by Kew (1734) as «quinque paria 
ossiculorum, sinubus maxillarum applicanda». This must have been overlooked by J. MOLLER 
when he credited Parra with the first complete account of the jaw-skeleton. 
* For the literature briefly referred to in this section, see the bibliography in Bronn’s «Thier- 
reich» II, Abth. 3, pp. 971—1001; 1901. 
Resultate der wissenschaftl Erforschung des Balatonsees. I. Bd. 1. T. Pal. Anh. 9 
