Gill NKW YORK STATD MUSEUM 



the (Cjilialdpod ImmIv, \hv following!: obstacles nnist first be 

 (•It'arcd awav: li 'I'Im\v arc usually (Miuiplctcly <lis<^(>cia(iMl from 

 tlie Vephalopod slu'lls. -) Sonio I'oruis ol' l>isriu(»raiis and Pclto- 

 caris of tlw early Siluric are \irlually indlslliijiuisliable save 

 f<U' outliuo and size I'loiii Spalliioearis and Cardiocaiis of (he 

 Devonie. Tlio former ap])eared ai a lime lou«^ auleeedent to 

 the ammonoids. A\'e know llia( eiie (»t' thus*' early species was 

 brachiopodous, lln' olhers are not gonial it ine; the later forms 

 can hardly match our conception of bi'achiopod structure. Ob- 

 jects of so similar a cliaracter \>()uhl <i priori be of similar nature, 

 an ar<i:ument wliich, if cariied to a lo«;ical conclusion, wouhl 

 wreck tlu' int'eiied jioniatitine character of the DeNonic f^enera. 

 In moetin^^ these obstacles it is to be borne in mind that no sin- 

 gle specimen of any of the jicnera l>iscinocaris, Pholadocarit*, 

 Spathiocaris, Cardiocaris has been i>roved crustacean. The seg- 

 ments and spines referred to these may or may nut have any 

 relation to the shields themselves. 



There is a series of these shields wliich is unlike those 

 specially mentioned above, in having a triangular cleft at both 

 extremities, that behind not reaching to the apex or growth 

 center of the surface, but often broader than the anterior cleft. 

 These are wholly Devonic objects and have been termed 

 by the writer J)ipt<'rocaris. American specimens have be<n 

 found not so mn4-h in the biluminons lay<'rs of the upper 

 Devonic as in the flags and sands, and c(M*tain specimens have 

 clearly indicated that in uncompressed condition the contour 

 was distinctly sloping from the bridge between the two lateral 

 wings of the shield. Among these specimens there is no room 

 for any suspicion that they have brachioi)odons affinities. 

 Regarded as Crustacea, that is Phyllocarida, at the time of the 

 description of tin* genus, the crustacean similarities are indeed 

 more strongly niaiiN<'<j iluiii in (lie Spathiocaris class of 

 shields, a feature specially brought out on comparison between 

 such a 1 >iiMcinr;iris anil I lie carajKHe of a jtliyllocarid like 

 Khinocaris or Mi'solliyra; bui <ui the other hand the gen- 

 eral form, structure and surface characters of all these 



