356 



GENERAL SUMMARY TO 



Sttb-Fahilies and Genera. 



Generic position and family 

 still undetermined. 



J ? Triplesia, Hall, 1859 . 

 \ ? Streptis, Dav., 1881 ' 



V. Family Pobambonjtid.2E, Dav., 1853. 



Zittel places Meek's genus Syn- ~\ 

 trielasma with the Porambo- 



nitidcB.WhQthcrPorambonites I „ , ., _ , .... 



, , , ... . ,. ,. . > Forambomtes, Pander, 1830. 



should constitute a distinct \ 



family has still to be deter- 

 mined. J 



VI. Family Oethisid^;, a" Orbigny. 



Orthis, Dalman, 1828 



Enteletes, Fischer, 1837 .... 



= Syntrielasraa, Meek. 

 ? Schizophoria, King, 1850 . 

 Skeuidium, Hall, 1860 



T 



In this family several other so- 

 termed genera have been in- 

 cluded. Bayle adopts Schlo- 

 theim's generic name Hystero- 

 lithus for such shells as O. 

 resupinaia. A genus Bis- 

 ccelosia was proposed by King 

 for Orthis biloba and Plati- 

 strophia for O. biforata. 



specimens as many as from six to eight of the smaller cells may be seen in the wall around each larger 

 hexagonal cell, one being generally situated in each of the angles, and sometimes one between ; but, as already 

 stated, they do not appear to reach the outer surface of the shell in perfect or unworn specimens. The third 

 or innermost layer of the shell is the dense portion that is perforated by minute circular tubes. These 

 tubes are small, as those in the shell-structure of the Carboniferous Dielasma (Terebratula) hastata, but 

 they are only about one third as numerous as seen in that shell. They agree in character with that 

 seen in many other of the Brachiopoda, but the outer shell-layer of E. Capewelli is so unlike what is 

 known to exist in this group that one is not surprised to learn that it has been suspected to be of 

 Polyzoal origin, and the resemblance of the cell arrangement to that seen in some forms of Monticulipora 

 is further increased by finding that the outer cell-walls enclose a series of small polygonal cells, as is 

 common in some members of this group. In a vertical section through both valves and from fragments 

 picked up from the shale I find that the outer celluliform layer is just about equal in thickness to that 

 of the dense inner layer of the shell." Mr. Young believes that the bare part of the beak, which I have 

 already described in my Monograph, was probably attached to marine objects and afterwards broken away 

 from its attachment, for besides the rough ragged edges of the shell layer there is no finish to the edges of 

 the cells. Mr. Young remarks likewise that Prof. Lindstrom notices only two layers, but that there exists 

 a third or thin outer one that form3 the external hexagonal cells, and which when present and perfect 

 conceals the inner small polygonal cells. 



1 Much uncertainty still prevails with respect to the family into which the genus (?) Streptis should be 

 classed. Its interior characters are difficult to determine, and well-preserved interiors of the valves and 

 internal casts have still to be discovered. At my request Mr. John Young ground down and made 

 sections from a number of promising specimens I had obtained from Mr. Maw's washings of Wenlock 

 Shale, but he could discover in them not a trace of a loop or of spirally-coiled appendages. 



