February io, 1893.] 



SCIENCE. 



73 



of the direct obolelloid derivation of the palaeozoic Lingidce from 

 Obolella. Lingulella and Lingulepis, forerunners of Lingula, may 

 be found to be important connecting links, having the outward 

 form of linguloids with the muscular ariangements and narrow 

 pedicle slit of the obolelloids. "The development on the lingu- 

 loid line has continued, as we believe, from early Silurian to the 

 present time with frequent modifications. From Lingula we 

 may depart in many directions. In Lingulops and Lingulasma 

 we get indications of physiological influences on the origin of 

 genera.'" 



It appears that "augmented muscular energy and concomitant 

 increased secretion of muscular fulcra" with the large size and 

 consequent displacement of the liver induced the thickening of 

 the entire area of muscular implantation. Gradual excavation 

 of this solid plate ensued, and the formation of a more or less 

 vaulted platform, extremely developed, in the feebly articulated 

 Trimerellids of those Silurian seas, which favored the rapid de- 

 velopment of the platform-bearing jBrachiopoda, a race which 

 was abruptly exterminated at the close of the Niagara and Wen- 

 look period. Hall's new genus, Barroisella. is a divergent so 

 marked by the development of deltidial callosities as to indicate 

 their approximating specialization for articulating and interlock- 

 ing purposes. Thus we get most striking evidence of a tendency 

 to span the interval between the so-called edentulous Inartimlata 

 and the articulated genera in the Linguloid and Trimerelloid 

 groups. 



The genus Obolus is shown to be more specialized than O&oZdZa, 

 less so than Lingula, Neobolus being an intermediate form with 

 cardinal processes, also indicative of progress in this direction 

 towards the Articulata. In Obolus, however, the muscular scars 

 are excavated as in LiKgj/?Cf, not elevated as in the forms tending 

 to Trimerella. Thus we get indications in the history of the an- 

 cestral Trimerellids of the attainment of a like remarkable I'e- 

 sultant along distinct lines of development, of which another 

 Instance has been furnished by Messrs. Fischer and Oehlert's re- 

 cent studies of the development of the living Magellance of the 

 boreal and austral oceans, to which we had elsewhere occasion 

 ti refer. ' As Hall and Clarke's generalizations are formulated with 

 a due regard to geological sequence, they possess more validity 

 than the phylogenetic deductions enunciated by a Teutonic palaeon- 

 tologist, in which that important factor was somewhat neglected. " 

 " We have yet to seek," the American brachiopodists conclude, 

 "the source whence these numerous closely allied primoidial 

 groups are derived, in some earlier comprehensive stock of which 

 we have yet no knowledge. The ages preceding the Silurian 

 afforded abundant time for a tendency to variability to express 

 itself" (p 168). 



From this satisfactory discussion of the origin and development 

 of the palaeozoic unarticulated genera and species. Hall and 

 Clarke proceed to consider the structure and relations of the far 

 more numerous and more complicated order of the articulated 

 species, and commence with the Ortholds, the lowest forms of the 

 Articulata, as. by common consent, they are now regarded. The 

 allied Strophomenold, Streptorbynchoid. and Leptaenolds, as de- 

 fined by Dalman, are then treated of and the first part terminates 

 with a discussion of some carboniferous Productoids. The spire- 

 bearers, Rhynchonelloids and Terebratuloids, of the Palseozoic 

 seas are thus left for the concluding volume, when we may look 

 for a valuable general summary of results and for that systematic 

 classification, based on their completed investigations, which the 

 authors are bound to propose in the interest of students for the 

 root, stem, branches, and twigs of the genealogical tree of the 

 Brachiopoda, as they have definitely abandoned the family names 

 hitherto in vogue. It must certainly be admitted that brachiopo- 

 dists have often found it difHcult, and sometimes impossible, to 

 determine to which of two well characterized families certain 

 annectent forms should be definitely referred. 



In Europe, however, the retention of family designations is 

 not always considered incompatible with the modern philosophical 

 and evolutional methods of class treatment. They have been 



' On the Distribution and Generic Evolution of Some Recent Bracliiopoda, 

 By Agnes Crane, Naturai Science, January, 1S93. 



5 Neumayr, "Die Stiimme des Tlilerrelelis Brachiopoda," 1890. 



preserved with advantage; for instance, in Mr. A. Smith Wood- 

 ward's ' masterly systematic classification of the fossil fishes in 

 the British Museum, and also in Professor W. A. Herdman's'' ex- 

 haustive report on the Tunioata dredged by the ''Challenger" 

 expedition, associated in this case with evolutional data and the 

 presentation of numerous pbylums showing the interrelations of 

 genera, somewhat after the same plan as that adopted in the 

 "Introduction to the Study of the Palaeozoic Genera of Brachio- 

 poda. " With all due respect to the veteran of the old school and 

 the disciple of the new, we venture to submit the imposs-ibility 

 of impressing on the mental retina a permanent photograph of 

 the innumerable and fascinating phylums which they have pro- 

 vided with such industrious research. But we are not all en- 

 dowed with so much insight, knowledge, and experience. 



The most revolutionary feature in the present instalment of 

 their researches on the Articulata is the extreme subdivision to 

 which the great group of Orthoids has been subjected. The 

 genus Orthis is absolutely restricted to eight species (instead of 

 two hundred), with O. callactis of Dalman as the type, and his 

 early figures and original descriptions are judiciously reproduced 

 for the benefit of American students. Theremainder of the large 

 number of species are placed under various new genera and sub- 

 genera, or restored to their former appellations. For instance. 

 Pander's name, Clitambonites, is once more applied to species un- 

 justly usurped by D'Orblgny's Orthisina. and Plectambonites of 

 the same Russian palaeontologist is restored for the Palaeozoic 

 species grouped by the French conchologists and those who fol- 

 lowed them under the genus Leptaena of authors not of Dalman, 

 The Leptaena rugosa of this author is taken as the type of 

 his genus, the scope of which is thus much restricted, and new 

 generic names are proposed for several of the species indifferently 

 described as Strophomenas or Leptaenas by various authors. 

 Linne's sub-genus Bilobites is revived for those abnormal bilobed 

 species of Orthis, which, according to Dr. Beecher's investiga- 

 tions, originated from a normal form at the adolescent and 

 mature stages of growth in both direct and indirect lines of de- 

 velopment. In view of the extensive breaking-up of the Orthoids, 

 here proposed, into several genera and sub-genera, we are willing 

 to confess that to object to the revival of Bilobites would be but 

 straining at a gnat and swallowing the camel. We, however, 

 admit a preference for those among the proposed new or restored 

 designations which give some indications of the former position 

 of the species among genera. Such are Protorthis, Plectorthis, 

 Heterorthis, Orthostrophia, Platystrophia , and so on. Orthidium 

 for the generic divergent nearest allied to Strophomena seems a 

 less happy selection. Tabular views, both instructive and sug- 

 gestive, are given to show the approximate range in the geological 

 horizons from the calclferous shales of the Lower Silurian to the 

 Upper Coal Measures which indicate the appearance, persistence, 

 and extinction of the various genera into which, under new, old, 

 or restored appellations, the Orthoids, Strophomenoids, and Lep- 

 taenolds are sub-divided — a sub-division which, with its asso- 

 ciated shifting of types will not escape criticism. 



There will always be differences of opinion respecting generic 

 values. Here, as Heckel long ago pointed out, the personal 

 equation becomes prominent. We believe Professor Cope was 

 the first to advance the then heterodox view that species could be 

 transferred from one genus to another without affecting their spe- 

 cific characters. Many so termed genera represent what have now 

 become abbreviated transitional phases in the development of the 

 race which, of old time, became stereotyped for periods of longer 

 or shorter geological duration. The researches of Friele and 

 Oehlert on the recent Magellanae {Waldhumia) the ultimate 

 phase of development of the long-looped branch of the Terebratu- 

 loiiis, illustrate this point most clearly. If the inter- relationships 

 and passages of these generic phases are carefully noted, they 

 become so many illustrations of one method of the evolution of 

 genera, which, sometimes, it is evident, originated from causes 

 incidental to individual development, accelerated growth, and the 

 circumstances of the environment. 



3 A Catalogue of the Fossil Fishes in the British Museum, Part I., 1889 : 

 Part II., 1890. 



■I Reports'of the "Challerger" Espedltton: Tunicata, vols, vi., siv, and xxvl. 



