366 GENERAL SUMMARY TO 



According to Dr. Waagen's views the family Thecideidce, would comprise : 



1. Sub-family Megalhyrina, Dall; including Argiope, Desl, Cistella, Gray, Zellania, 

 Moore. 



2. Sub-family Thccideince, Dall ; including Thecidea, Defr., and Pterophloios, Giimbel. 



3. Sub-family Lyttoniince, Waagen; including Lyttonia, Waagen, Oldhamina, Waagen. 

 And he adds that the sub-family Megathyrida would be a convenient transitional 



link between the Tercbratulidce and the Thecideidce. This may be so, but I am not yet 

 prepared to include the Megathyrina as a sub-family of T/iecideinee, and would prefer, 

 at least provisionally, to leave Argiope, Cistella, and Zellania as a sub-family of the 

 Terebratulidce. 



In a very instructive paper, entitled " Note sur quelques especes nouvelles de 

 Megathyrides," 1 M. G. de Morgan strongly urges the adoption of A. d'Orbigny's 

 generic name Megathyris, 1847, in preference to that of Argiope, E. Desl., 1842, on 

 account of the generic name Argiope having been previously given by Latreille to a genus 

 of Spiders. 



In 1853 Count Keyserling described a fossil from the Carboniferous Limestone of the 

 Ural under the name of Thecidium filicis, which was subsequently figured by Moller 

 in the ' St. -Petersburg Mining Journal.' * 



Sub-family— LYTTONIINCE, Waagen, 1883. 



" Shell of large size, flat or vaulted, attached by the larger valve ; hinge-line straight 

 but short, no area or pseudo-deltidium ; internally, the ventral valve with a median and 

 numerous lateral septa ; dorsal valve rudimentary, forming together with the brachial 

 apparatus one strongly-lobed shelly plate, which fits between the external septa of the 



1 ' Bulletin de la Societe Zoologique de France,' vol. viii, 1883. The author remarks " that with the 

 Megathyris as well as with the other Brachiopoda the long and flexible cirri, with which the two membranous 

 appendages are garnished, are destined to produce in the water a disturbance which draws the nutritive 

 particles to the mouth of the animal. Nevertheless, in this group of animals one can discern neither 

 special buccal whirlwinds nor any fixedness in the direction of the currents or flow of the particles 

 attracted towards the brachial disc ; they show a tendency to go to the centre notwithstanding that the 

 mouth is eccentric, then they are rejected in any direction, and return now and then to the same place 

 after having at several renewals made the round of the apparatus. However, the septums of their shells 

 force back before them the cirri and tend to disturb this equilibrium. The Megathyrides (or Argiopes) 

 are, if we credit M. J. Herouard, the worst organised of the Brachiopoda with respect to nutrition ; 

 therefore the author in his classification of the genera with regard to their nutritive faculties places them 

 in the last rank after the Thecideidce, whose apparatus, although analogous, produces very different 

 effects." In this paper M. de Morgan gives the list of all the species of Megathyris (or Argiope) and 

 Cistella known to him. The paper is illustrated by a well-drawn plate and by many woodcuts. 



2 "Description of the Carboniferous Brachiopoda of the Ural," 'Annales des Mines Russes,' vol. iv, 

 1862. 



