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NEW YORK STATE MUSEUM 



111 several respects one of the most peculiar genera here under investi- 

 gation is Lasiograptus. Its species usually appear as rather lax rhabdo- 

 somes with apertural spines or fibers [pi. 29, fig. 9-14], which often reached 

 considerable length and sometimes are observed to connect with each other. 

 At times also larger subtriangular appendages have been observed which 

 suggest cystlike organs and have been considered as gonangia. We have, 



on the strength of some very favorably preserved speci- 

 mens, attempted here a reconstruction [pi. 31, fig. 5] 

 according to which the fibers, triangular appendages 

 and shreds of fine network are parts of outer continua- 

 tions of the thecae. In this group either the reduction 

 of the periderm of the thecae has affected but the distal 

 halves of the thecae on the lateral sides, or an original 

 spinosity has led to the development of an outer pro- 

 tecting structure permitting a safe longitudinal growth 

 of the zooids. 



In the discussion of the genus Lasiograptus in this 

 memoir the details of the structure of Lasiograptus are 

 more fully described and several reasons advanced for 

 the view that the reticulate outer structures are new 

 acquisitions of the genus. The principal of these rea- 

 sons are the astogenetic development of the rhabdosome 

 [see pi. 29, fig 16] which indicates a later appearance of 

 the outer reticulate structure than the inner halves, and 

 the relations obviously existing between Climacograptus retio- 

 loides and Lasiograptus. The former species, as set forth more fully 

 under Lasiograptus, possesses horizontal bandlike thickenings of the 

 middle layer of the periderm [see text fig. 50J which are connected with 

 recurving loops proceeding outward from the ventral walls. Like hori 

 zontal ledges are seen in macerated specimens of Lasiograptus [pi. 20, fig 

 1 5 I 1^- 3°< fig- 2 > 7} ;ul( l the loops of C. retioloides quite obviously 

 correspond to the fibrous loops on which the distal structures of Lasi. 



Fij*. 50 CI i mac ograp t u 

 retioloides Wiman. x 3 

 (Copy from Wiman) 



