Dr. W. B. Carpenter on the Structure of Brachiopod Shells. 503 



Having been requested by Mr. Davidson to contribute a 

 Memoir on the intimate structure of the Shells of Brachiopoda 

 to his admirable Monograph of that group in course of publication 

 by the Palseontographical Society, I re-entered upon the in- 

 vestigation with no desire but that of contributing to the esta- 

 blishment of the truth ; and made microscopic sections of many 

 additional specimens, with which Mr. Davidson kindly supplied 

 me, — the total number of sections examined (nearly all of which 

 are preserved in my cabinet) being about three hundred. In the 

 course of this inquiry, the presence of perforations in Terehratu-, 

 lidce, and their absence in Rhynchonellidce, was established as the 

 character of so large a number of species of both tribes, that I 

 thought myself justified in stating these as distinctive characters 

 of the shells of these two groups respectively. A remarkable 

 confirmation of their validity, and an important lesson as to the 

 fallacy of superficial observations upon this point, were afforded 

 by the apparently-exceptional cases of Striyigocephalus and Por- 

 ambonites. The former had been previously regarded as a non- 

 perforated genus, and had been associated on other grounds 

 with the Rhynchonellidce ; examination of microscopic sections, 

 however, satisfied me that its shell was perforated; and the 

 letter in which I communicated to Mr. Davidson this at first 

 sight anomalous fact, was crossed by one from him to me, men- 

 tioning that he had been led by the researches of Prof. Suess to 

 consider the affinities of Stringocephalus as being rather with the 

 Terebratulidce, and inquiring as to the presence or absence of 

 perforations; so that both sets of characters came again into 

 complete harmony. The place of Porambonites being undoubtedly 

 among the Rhynchonellidce, the existence of perforations (which 

 had been thought to be unmistakeably indicated by the very 

 regular punctations of the surface) was an apparent anomaly of 

 no small importance ; this, however, was at once removed by 

 the examination of microscopic sections of the shell, since it was 

 found to be as destitute of perforations as any true Rhynchonella. 

 The case of Trematis was one of the same kind, the punctations 

 being there also quite superficial ; constituting, in fact, a peculiar 

 kind of ' sculpture.' 



I thought it right, in stating these and similar facts, to give 

 an emphatic warning against superficial observations upon this 

 point, and to express my surprise that Prof. King should have 

 ventured, upon such evidence, to affirm the universal existence of 

 perforations in the shells of Brachiopoda; especially without 

 having examined one of the most common of the recent types of 

 the group, namely Rhynchonella psittacea, in which the absence 

 of perforations, as described and figured by me in 1844, can be 

 verified without the slightest difficulty. " To myself personally," 



