BRACHIOPODA. 



BRACHIOrODA. 



Hurt in i. 



2. The lateral parts of the support formed of a very fine spiral fila- 

 ment, BO as to produce two hollow somewhat conical mantes which 

 nearly fill the whole of the shell. 



Genus Spirifrr, Sowerby. 



Kxample, Spiri/er tnyamalit (fossil). 



Inlrrnal view of Spirifrr trigoaalh, showing the npiral procwson. 



E. The upper valve opcrculiform or very flat, system of support 

 beginning to disappear. 



1. Upper valve very flat 

 Genus Maya*, Sowerby. FosaiL 

 Example, M ayat pumiltu. 



Ifagal fumilus. 



1. Upper valve very much excavated above, summit of the lower 



valve not pierced, and divided into two nearly equal parts by a 



well-developed mesial furrow. 



Genus Product*, Sowerby. Fossil. (See ' Min. Con.,' pi. 320.) 



Example, Producta Martini. 



Proditcla Martini. 



Th fossil Tertbratufa (properly so called) are extremely numerous, 

 and aasist in the identification of strata from the supracretaceous 

 group to some of the lowest formations in the grauwacke series, both 

 inclusive. 



As neither Penlattera, Strygocephalui, Spiri/tr, Magat, nor Producla 

 has living representatives, they are placed here from the structure 

 of their shells, which, judging from analogy, would indicate a brachio- 

 podoui construction allied to Ttrcbraiula. Indeed De Blaiuville 

 retain* that name throughout ; but we think the differences of con- 

 formation warrant the separation of the fossils above distinguished, as 

 ubgrncra of the Trrtbrululinit. They occur principally in the more 

 ancient fossil iferous beds. 



Thttidea, Defiance (TheciJiim, Sowerby). De Blainville thus 

 describes the genus : " Animal entirely unknown, but very probably 

 differing but little from that of Orliimla. Shell equilateral, regular 

 very inequivalve, and sufficiently similar to the Tcrtbralula of the 

 latter sections ; one valve hollowed, the heel or hook recurved, entire 

 without a fiwurc and adhering ; the other flat, operculiform, and with 

 out any trace of the internal support 



Hinge longitudinal ; articulation by two distant condyles, as in the 

 Ttrebnttulir, with a large mesial tooth in the flat valve fitting between 

 the condyloid teeth of the concave valve. 



Kxample, Thrciilium railiitum. 



The recent species above mentioned is an inhabitant of the Meditcr 

 ranean, and found among the common red coral of the Tuscan seas. 



The fossil species are tolernUy numerous, and Sowerby says thn' 

 those which he had seen ap|>eared to belong to the chalk, and were 

 brought fmm Maastricht, and from Orglande* in Normandy. 







ThfciJium raJiatum, rlfwed from al en. a, nat. tin, 



Lingula (Brugieres). Shell subequivalve, equilateral, depreMed, a 

 ittle elongated, truncated anteriorly ; the summit mesial and poste- 

 rior, with no trace of a ligament, but j.-im-a at tin- .xtremity to u long 

 ibro-geUtinouK peduncle, which is supposed to fix it vertically to 

 submarine bodies ; but in the specimen of Linyuln Aadfbardii exa- 

 iiini-d by Mr. Owen, there was no trace of the adhesion of any foreign 

 body to the end of this peduncle. Muscular impressions multiple. 

 Kxample, I.itujnln analina. 



Lingula analina. 



The recent species have been found at depths ranging from the sur- 

 face to seventeen fathoms ; and specimens have been taken in hard 

 coarse sand from four to six inches below the surface of the saml. 



Lingnla has been found in :i fossil state in the Inferior Oolite of 

 Yorkshire, in the Old Red-Sandstone formation, and in other old fos- 

 sil iferons beds. 



mropHamtna, Rafinesque (fossil). Shell regular, equilateral, sub- 

 equivalve; one valve flat, the other (lightly axatvated : artim' 

 straight, transverse, with a small projection notched or dentelated 

 transversely. No trace of an internal support. 



Example, Strophomtna ragout. 



Xlraphomma rvgota. View of lower dido. 



As Rtraphomtna has no living representatives, at least none yet dis- 

 covered, there can be no description of the aniiiml, \vlii.li K howrvrr. 

 judging from the construction of the shell, most prolnbly br:i 



The fossil generix 1'layivttoma, Uianclutra, and f'vtloptit are placed 

 by De Blainville under this section. [PLAGIOKTOXA ; DIANC IK.IIA ; 

 PoDOPBU.] We do nut however think that there is such pregnant 

 evidence of a true ami rut in- l>r.irliipodoua organisation as to w.irnmt 

 this decided position under the Bnxchiopods. Imlr.-<l I>. llhiiuvillr 

 himself says that some of the /V(i</i<'.,iM w ..f (li.- family / 



ihlthat the others (he instances Plagiot'oi.. 'ii) are 



entirely different, and he allow* that these lant ought to form a dis- 

 tinct genus of the family of Subostroceans. Uefraiice places 1'odoptit 

 among the oysters. 



