1883.] 31 3 [Hyatt. 



Cloiochoanites. 

 [Transitiones.] 

 The transitional forms of the Goniatitinae, which have the short 

 type, or partly cloiochoanitic funnel elevated upon a median 



the ovisac. These are the remants of the nmbilical perforation, which are present 

 in the young of all other close coiled Ammonoids. These characteristics, and the dor- 

 sal position of the siphon, and the presence of deep annular lobes, are differences of 

 great importance and show that we must place the series above the Nautilinidae. The 

 forms are evidently highly concentrated in development, but descendants probably of 

 the same stock as Anarcestes. The adult forms and the sutures of Cyrtoclymenia are 

 very similar to those of Anarcestes and indicate this derivation. The group appears 

 to have had a very narrow distribution chronologically and geographically, and was 

 probably a highly specialized series with exceptionally rapid evolution in some open 

 fields of the Devonian. So far as I know, not a species of this group has yet been 

 found in North America, those described heretofore are now known to be Goniatites. 

 The author has spent considerable time in the study of this group and divided them 

 into genera, but these can only now serve as the basis of appreciative criticism for the 

 elaborate work of Dr. Gumbel, Ueber Clym. Paleontog. Vol. 11, p. 83, 1863. This 

 author's sub-groups are equal to our genera, and most of his varieties are what we 

 should call species. We, therefore, use his names in this value without making any 

 claim to the credit of having originated them. This extraordinary series shows the 

 phenomena of quick evolution in three series of forms. Cyrtoclymenidae with a series 

 beginning with an Anarcestes-like form and passing through discoidal and compressed 

 to quadragonal costated forms. Cymaclymenidae, a similar parallel series but with more 

 complex sutures, and Gonioclymenidae also a similar series, but with more involute 

 forms than the last, and the sutures becoming ammonitic with median ventral lobes 

 and saddles divided by a pair of marginal lobes. The whole range of the transformations 

 of the Goniatitinae are paralleled in this short series, whose principal differential charac- 

 teristic is the dorsal position of the siphon. We have had no opportunity of studying 

 the siphon but Dr. Gumbel's group of Euclymenia with imperfect siphons appear to 

 us like the imperfect siphons which occur not infrequently among Nautiloids, the con- 

 nective wall being destroyed by maceration. The Nothoclymeniae are apparently those 

 with longer, larger funnels and thicker connective walls. Dr. Gumbel's figure of Cly. 

 speciosa gives the funnels as if terminated by a darker colored connective wall. 



CYRTOCLYMENIDAE. 



The sutures are simple with broad undivided ventral saddles, rounded or incomplete 

 shallow lateral lobes and only rarely internal saddles on the sides. The siphon is tubu- 

 lar and small. 



Cyrtoclymenia includes species with depressed semilunar whorls in section, similar 

 to those of Anarcestes. The sutures are similar, but the ventral saddles of the 

 Clymeninae are present, though rounded, and the lateral lobes are also rounded. Type , 

 Cyrt. angustiseptata, Gumb. pi. 15. 



Oxyclymenia includes forms with discoidal shells, compressed and more or less in- 

 volute whorls. The larval depressed whorls of Cyrtoclymenia have disappeared from 

 the adult stages. The sutures have ventral saddles more prominent than in that genus, 

 and in some species the angular lateral lobes are deeper, but there are no large lateral 

 saddles. Type, Oxy. laevigata, ibid, pi. 16, also undulata, pi. 17, and Dunkeri, pi. 16. 



