157] PROTEOCEPHALIDAE—LA RUE 157 



Vagina always anterior to cirrus-pouch, never crossing the latter. 

 Beginning region of vagina narrow. This region about 0.1 mm. long, 

 terminated by weak sphincter vaginae. Adjacent to narrow region a 

 dilated portion. Vagina not ciliated in any part of length. Vesicula 

 seminalis present. Vitellaria with large follicles, not paralleling pos- 

 terior margin of proglottid. Uterus when fully developed with 20-25 

 lateral outpocketings on either side. ^ Uterine pores ventral, 2-3-4 in 

 number. Eggs with three membranes. Embryos 0.014-0.0156-0.0168 

 mm., second membrane 0.026-0.031 mm., outer membrane 0.027-0.033 

 mm. in diameter. Excretory system has four main lateral trunks. 

 Ventral vessels large, dorsal vessels much smaller. All main vessels 

 sinuous or spiral. Many secondary openings to exterior. 



Habitat: In intestine of Lepisosteus platostomus (type host), Illi- 

 nois river, Havana, Illinois (type locality). 



Type: Alcoholics No. Ha 30 i and slides from same. Cotypes, 

 Ha 12 d, e ; Ha 29 f ; Ha 87 a ; Ha 88 a ; Ha 101b ; Ha 110c. Mate- 

 rial in Dr. H. B. "Ward's collection. 



La Rue (1911:479) in a preliminary way described this species. 



In a collection of endoparasites secured by Dr. H. B. Ward from 

 fish caught in the Illinois river at Havana, Illinois, were some speci- 

 mens of Proteocephalus somewhat resembling the species which the 

 writer (1911) has designated as P. perplexus. On account of the pecu- 

 liar form of the head and suckers of this species the name Proteoceph- 

 alus singularis La Rue has been proposed for it. In all, eight gars were 

 examined. Of this number only one was uninfested with this parasite. 

 This gar was infested only with P. perplexus. The numbers of P. sin- 

 gularis present in each of the seven infected hosts were : 2, 7, 26, 2, 5, 

 4, 8. Two gars had a mixed infection of P. singularis and P. perplexus. 

 Slides have been prepared from some of this material. 



Its study showed that the longest piece measured 170 mm. Com- 

 plete strobilas perhaps measure up to 250 mm. or more. Its maximum 

 breadth is about 0.90-1.00 mm. The strobila is slightly smaller than 

 that of P. perplexus yet it greatly resembles the latter species in out- 

 ward appearance. The more slender neck and the smaller head are 

 its more readily noted points of difference. The head (Figs. 24, 25) is 

 small, measuring from 0.250 to nearly 0.300 mm. in breadth by 0.20- 

 0.22 in length. At its broadest part it bears four large suckers which 

 when well expanded cover up nearly the whole surface of the head 

 except the apical region. The apical region in most species is flattened 

 or conical, but in this species it is drawn out into a long slender pro- 

 tuberance which has no hooks. This is not a rostellum. At times this 



